Update "ACTUALLY skipped by" comments

The remaining "ACTUALLY skipped by" comments in the test suite were
for tests that are actually skipped by SkipTest exceptions raised
from the code under test. But the information provided about where
in the code they were skipped was out of date, and also not
detailed enough because references to line numbers become stale
when code is added or removed in the referenced module before the
referenced code.

This updates them and also provides more detailed information about
the referenced code doing the skipping.

The error messages are the same as before, and the paths are the
same in relevant details, so this doesn't modify those parts of the
comments.

test/test_docs.py

@@ -21,7 +21,10 @@ def tearDown(self):
 
         gc.collect()
 
-    # @skipIf(HIDE_WINDOWS_KNOWN_ERRORS,  ## ACTUALLY skipped by `git.submodule.base#L869`.
+    # ACTUALLY skipped by git.objects.submodule.base.Submodule.remove, at the last
+    # rmtree call (in "handle separate bare repository"), line 1082.
+    #
+    # @skipIf(HIDE_WINDOWS_KNOWN_ERRORS,
     #         "FIXME: helper.wrapper fails with: PermissionError: [WinError 5] Access is denied: "
     #         "'C:\\Users\\appveyor\\AppData\\Local\\Temp\\1\\test_work_tree_unsupportedryfa60di\\master_repo\\.git\\objects\\pack\\pack-bc9e0787aef9f69e1591ef38ea0a6f566ec66fe3.idx")  # noqa E501
     @with_rw_directory

test/test_submodule.py

@@ -457,7 +457,10 @@ def _do_base_tests(self, rwrepo):
             True,
         )
 
-    # @skipIf(HIDE_WINDOWS_KNOWN_ERRORS,  ## ACTUALLY skipped by `git.submodule.base#L869`.
+    # ACTUALLY skipped by git.util.rmtree (in local onerror function), called via
+    # git.objects.submodule.base.Submodule.remove at "method(mp)", line 1018.
+    #
+    # @skipIf(HIDE_WINDOWS_KNOWN_ERRORS,
     #         "FIXME: fails with: PermissionError: [WinError 32] The process cannot access the file because"
     #         "it is being used by another process: "
     #         "'C:\\Users\\ankostis\\AppData\\Local\\Temp\\tmp95c3z83bnon_bare_test_base_rw\\git\\ext\\gitdb\\gitdb\\ext\\smmap'")  # noqa E501