Remove git status assert

On CI, there is an uncommitted file `RELEASE.md`, so the output looks
like this
```
M pyproject.toml
?? RELEASE.md
```
causing our assertion to fail.

A possible fix would be to pass `--untracked-files=no`.
However, it seems more straightforward to just remove the assert.
Callers should refrain from abusing `SDIST_IGNORE_DIRTY`, though.

setup.py

@@ -106,8 +106,6 @@ def run_setup(modnames, pl_name, pdfium_ver):
             if helpers_info["dirty"]:
                 # ignore dirty state due to craft_packages::tmp_ctypesgen_pin()
                 if int(os.environ.get("SDIST_IGNORE_DIRTY", 0)):
-                    status = run_cmd(["git", "status", "--porcelain"], capture=True, cwd=ProjectDir).strip()
-                    assert status == "M pyproject.toml"
                     helpers_info["dirty"] = False
             else:
                 print("!!! Warning: sdist built without ctypesgen pin?", file=sys.stderr)

setupsrc/pypdfium2_setup/packaging_base.py

@@ -212,7 +212,7 @@ def parse_given_tag(full_tag):
 
     info = dict()
 
-    # TODO looks like `git describe --dirty` does not account for new committable files, but this could be relevant - consider evaluating dirty ourselves by checking if `git status --porcelain` is non-empty
+    # NOTE `git describe --dirty` does not account for new unregistered files
     tag = full_tag
     dirty = tag.endswith("-dirty")
     if dirty: