checks: Flake8 F841 fixes in the scripts directory part 2

[mshukuno]

Description

Flake8 F841 (local variable assigned to but never used) fixes in the scripts directory.

Motivation and context

Changes require resolving a part of Flake8 warnings that are currently ignored. The issue title and number as follows.

• [Bug] Fix currently ignored Flake8 warnings #1522

How has this been tested?

v.semantic.label
Removed unused as e from except. I don’t see this type of fix cause any issues. However, I tested with testsuit and all passed.

v.import
Removed unused tgtsrs value assignment and left gs.read_command("g.proj", flags="j", quiet=True).
With the GUI, I tried importing the data/all_types.gpkg and data/all_types_wgs84.gpkg files and encountered no errors.

Testsuit test_import_gpkg_wgs84 failed for self.assertVectorFitsRegionInfo. I don't see how this is related to F841 fixes, more likely GDAL version differences or something else. I personally find it no big deal since it's just a slight difference in reference and GUI worked just fine.

v.report
Removed unused line numcols = len(colnames) + len(extracolnames) . Tested with GUI since no testsuit. Worked fine.

v.unpack
Removed a variable assignment kept grass.read_command(…). Tested with testsuit and all passed.

Types of changes

Remove unused variables and/or entire lines when applicable.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing
  functionality to not work as before)

Checklist

It would be greatly appreciated if someone could point me to documentation on when to use "checks" prefix in PRs.

• PR title provides summary of the changes and starts with one of the
  pre-defined prefixes
• My code follows the code style
  of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.