Remove reversion.py (#20442)

It's dead, so let's remove it

Author: thejcannon

build-support/bin/classify_changed_files.py

@@ -37,7 +37,6 @@ class Affected(enum.Enum):
     "src/python/pants/init/BUILD",
     "src/python/pants/notes/*",
     "src/python/pants_release/release.py",
-    "src/python/pants_release/reversion.py",
 ]
 _ci_config_globs = [
     "build-support/bin/classify_changed_files.py",

src/python/pants_release/BUILD

@@ -3,9 +3,4 @@
 
 python_sources()
 
-python_tests(
-    name="test",
-    overrides={
-        "reversion_test.py": {"timeout": 90, "dependencies": ["3rdparty/python#pex"]},
-    },
-)
+python_tests(name="test")