l10n: it: fix spelling of "sorgente" (Italian for "source")

[jiangxin]

No description provided.

[github-actions]

Errors and warnings found by git-po-helper in workflow #924:

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ERROR [po/it.po@ee01097]	5013 translated messages. 
ERROR [po/it.po@ee01097]	too many obsolete entries (184) in comments, please remove them 
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ERROR [po/it.po@ee01097]	Found file-location comments in po file. By submitting a location-less 
ERROR [po/it.po@ee01097]	"po/XX.po" file, the size of the Git repository can be greatly reduced. 
ERROR [po/it.po@ee01097]	See the discussion below: 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	    https://lore.kernel.org/git/[email protected]/ 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	As how to commit a location-less "po/XX.po" file, See: 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	    the [Updating a "XX.po" file] section in "po/README.md" 
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WARNING [po/it.po@ee01097]	mismatched patterns: refs/heads 
WARNING [po/it.po@ee01097]	>> msgid: HEAD not found below refs/heads! 
WARNING [po/it.po@ee01097]	>> msgstr: HEAD non trovato fra i riferimenti/head! 
WARNING [po/it.po@ee01097]                           
WARNING [po/it.po@ee01097]	mismatched patterns: --dirstat=files,param1,param2..., --dirstat=files,parametro1,parametro2... 
WARNING [po/it.po@ee01097]	>> msgid: synonym for --dirstat=files,param1,param2... 
WARNING [po/it.po@ee01097]	>> msgstr: sinonimo di --dirstat=files,parametro1,parametro2... 
WARNING [po/it.po@ee01097]                           
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WARNING commit ee01097: author (Ruggero Turra <[email protected]>) and committer (Jiang Xin <[email protected]>) are different 
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WARNING commit ee01097: subject length 59 > 50, about 63% commits have a subject less than 50 characters 
INFO checking commits: 0 passed, 1 failed.        
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INFO downloading pot file from https://github.com/git-l10n/pot-changes/raw/pot/master/po/git.pot 
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ERROR [po/it.po@ee01097]	1649 new string(s) in 'po/git.pot', but not in your 'po/XX.po' 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	  > po/git.pot:545: this message is used but not defined in /tmp/2562154785--it.po 
ERROR [po/it.po@ee01097]	  > po/git.pot:597: this message is used but not defined in /tmp/2562154785--it.po 
ERROR [po/it.po@ee01097]	  > po/git.pot:602: this message is used but not defined in /tmp/2562154785--it.po 
ERROR [po/it.po@ee01097]	  > ...                   
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	826 obsolete string(s) in your 'po/XX.po', which must be removed 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	  > po/XX.po:562: warning: this message is not used 
ERROR [po/it.po@ee01097]	  > po/XX.po:624: warning: this message is not used 
ERROR [po/it.po@ee01097]	  > po/XX.po:691: warning: this message is not used 
ERROR [po/it.po@ee01097]	  > ...                   
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	You can download the latest "po/git.pot" file from: 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]		https://github.com/git-l10n/pot-changes/raw/pot/master/po/git.pot 
ERROR [po/it.po@ee01097]                           
ERROR [po/it.po@ee01097]	Please rebase your branch to the latest upstream branch, 
ERROR [po/it.po@ee01097]	run "git-po-helper update po/XX.po" to update your po file, 
ERROR [po/it.po@ee01097]	and translate the new strings in it. 
ERROR [po/it.po@ee01097]                           

ERROR: fail to execute "git-po-helper check-commits"