update issue templates

Author: pietroalbini

.github/ISSUE_TEMPLATE/missing-linux-packages.md

@@ -8,8 +8,9 @@ assignees: ''
 ---
 
 <!-- Thanks for reporting this issue!
-     Please remember our build environment is based on Ubuntu 18.04 LTS, so the
-     packages you're requesting need to be available in its repositories. -->
+     Please remember our build environment is based on Ubuntu 18.04 LTS,
+     so the packages you're requesting need to be available in its
+     repositories. -->
 
 **Affected crates:** foo, foo-sys
 **Ubuntu 18.04 packages to install:** libfoo-dev