Revert "Bug 1967634 - Apply fixes from python-sites lint r=ahal,mach-reviewers" for broken tests

This reverts commit b6bab59343.

Revert "Bug 1967634 - Add `python-sites` lint to facilitate adding rules specific to `python/sites/` r=ahal"

This reverts commit cd14d13cec.

Revert "Bug 1965905 - Remove `vendor_requirements.txt/in` as they are no longer necessary with `uv` python vendoring r=ahal"

This reverts commit dbb9b5ca9b.

Revert "Bug 1965907 - Re-enable `test_vendor.py` r=ahal"

This reverts commit c39a35d0a2.

docs/code-quality/lint/linters/python-sites.rst

@@ -1,40 +0,0 @@
-Python Sites
-==================
-
-This linter verifies that :searchfox:`python site <python/sites/>` files are
-following the best practices.
-
-Redundant Specifications
---------------------------------
-
-If a dependency is specified in the :searchfox:`mach site <python/sites/>`, it
-does not need to be specified in any command site (eg: `build.txt`, `common.txt`, etc).
-
-This check warns against these redundant specifications, and can also fix them.
-
-Specification Ordering
---------------------------------
-
-The first line of any site file should start with `require-python:`. All subsequent lines
-should be sorted alphabetically. This check ensures that's the case, and can fix the ordering
-for you, while still maintaining comment block association.
-
-Run Locally
------------
-
-This mozlint linter can be run using mach:
-
-.. parsed-literal::
-
-    $ mach lint --linter python-sites <file paths>
-
-Configuration
--------------
-
-This linter is enabled by default, and will run if you make changes to site files.
-
-Sources
--------
-
-* :searchfox:`Configuration (YAML) <tools/lint/python-sites.yml>`
-* :searchfox:`Source <tools/lint/python-sites/__init__.py>`