l10n: Update Catalan Translation for Git 2.51-rc2

Edit: We are continuing to follow the existing PO file convention, which
includes filenames but strips out line numbers from the file-location
comments. This standard was set by our former lead, Jordi Mas, and we
are maintaining it for project-wide consistency.

Signed-off-by: Mikel Forcada <mikel.forcada@gmail.com>
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>

Author: mlforcada