gh-98758: Fix unresolvable :exc: role in NEWS entry

shutil.ReadError has no documented exception entry in the docs
(only tarfile.ReadError does), so Sphinx's py:exc cross-reference
role can't resolve it, failing the Docs CI check. Use plain code
markup instead.

Author: SomSamantray

Misc/NEWS.d/next/Library/2026-08-11-19-05-00.gh-issue-98758.5S1Ijz.rst

@@ -1,4 +1,4 @@
 :func:`shutil.unpack_archive` now propagates the real underlying error
 (such as :exc:`FileNotFoundError` or :exc:`PermissionError`) when the
 input file is missing or inaccessible, instead of masking it with a
-generic :exc:`shutil.ReadError` about an unrecognized archive format.
+generic ``shutil.ReadError`` about an unrecognized archive format.