fix(scripts): let the guards pass valid updates

[noctuum]

An update was refused when the old version stood in a .SRCINFO line that does not take it from pkgver, as pkgdesc = A GPL-2.0 licensed tool at version 2.0, or when a SKIP checksum array held a comment or a backslash line continuation.

• check_prepared_srcinfo lets a line other than source keep its text or have the version replaced. A source line still must carry the new version.
• _pkgbuild_parts reads a comment and a line continuation in a checksum array as bash does. A backslash on the closing line, an escaped space before #, and )# stay refused.

bats tests/ --recursive: 402 pass.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
scripts/lib.sh	87.50%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!