pyoxidizer: disable the test for disabled & broken extensions help

The test is a bit fragile and the feature is significantly broken for 3rd party
extension already. So we disable that section with a comment about why and what
is needed.

Differential Revision: https://phab.mercurial-scm.org/D11304

tests/test-extension.t

@@ -1378,6 +1378,18 b' Disabled extensions:'
   (use 'hg help extensions' for information on enabling extensions)
 
 
+Help can find unimported extensions
+-----------------------------------
+
+XXX-PYOXIDIZER since the frozen binary does not have source directory tree,
+this make the checking for actual file under `hgext` a bit complicated. In
+addition these tests do some strange dance to ensure some other module are the
+first in `sys.path` (since the current install path is always in front
+otherwise) that are fragile and that does not match reality in the field. So
+for now we disable this test untill a deeper rework of that logic is done.
+
+#if no-pyoxidizer
+
 Broken disabled extension and command:
 
   $ mkdir hgext
@@ -1413,6 +1425,10 b' Broken disabled extension and command:'
   (try 'hg help --keyword foo')
   [255]
 
+#endif
+
+---
+
   $ cat > throw.py <<EOF
   > from mercurial import commands, registrar, util
   > cmdtable = {}