Update lucene syntax in search

[turhantolgaunal]

Since search will use it's own ANTLR based parser, the docs at https://docs.jabref.org/collect/import-using-online-bibliographic-database need to be updated in accordance.

[ThiloteE]

Since the linked PR was merged, now the docs could be updated. @turhantolgaunal are you on it?

[turhantolgaunal]

Ok, I will look into it.

[turhantolgaunal]

How should I change the since version part? This change isn't part of a specific version yet.