fix: read the omission line the installer writes

not_installable_words writes "436 files, 264 of them required. Why:
...": the count is followed by a comma, never a space, so the pattern
found no line and the test read the dry run as omitting nothing. The
page and the installer agree, the pattern did not follow them.

tests/test_doc_pages.py

@@ -137,7 +137,7 @@ class InstallerOutputExample(unittest.TestCase):
         manifest = json.loads((ROOT / "install" / "retroarch.json").read_text(encoding="utf-8"))
         # The line as the installer writes it (not_installable_words), or
         # its earlier "(1 required, not found: 37)" form.
-        omitted = re.search(r"Not installable: \d+ files? (?:\(\d+ required, (.*)\)\.|(?:is|are) "
+        omitted = re.search(r"Not installable: \d+ files?(?: \(\d+ required, (.*)\)\.| (?:is|are) "
                             r"not in the collection|.*Why: (.*)\.)", run)
         self.assertEqual(omitted is not None, bool(manifest.get("omitted_files")))
         if omitted and (omitted.group(1) or omitted.group(2)):