ci: remove obsolete Supported Python Versions replacement for Spanner

The templates now default to Python 3.10, so this workaround is no longer needed and causes AssertionError.

TAG=agy

CONV=acb0ee9b-3d87-4b9e-b3c6-0d4aa3efbd35

Author: suztomo

.librarian/generator-input/client-post-processing/spanner-integration.yaml

@@ -607,38 +607,7 @@ replacements:
       Next Steps
     count: 1
 
-  - paths: [
-      packages/google-cloud-spanner/README.rst
-    ]
-    before: |
-      Supported Python Versions
-      \^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^
-      Our client libraries are compatible with all current `active`_ and `maintenance`_ versions of
-      Python\.
-
-      Python >= 3\.9, including 3\.14
-
-      \.\. _active: https://devguide\.python\.org/devcycle/#in-development-main-branch
-      \.\. _maintenance: https://devguide\.python\.org/devcycle/#maintenance-branches
 
-      Unsupported Python Versions
-      \^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^\^
-      Python <= 3\.8
-    after: |
-      Supported Python Versions
-      ^^^^^^^^^^^^^^^^^^^^^^^^^
-      Our client libraries are compatible with all current `active`_ and `maintenance`_ versions of
-      Python.
-
-      Python >= 3.10, including 3.14
-
-      .. _active: https://devguide.python.org/devcycle/#in-development-main-branch
-      .. _maintenance: https://devguide.python.org/devcycle/#maintenance-branches
-
-      Unsupported Python Versions
-      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-      Python <= 3.9
-    count: 1
 
     # Note: noxfile.py is heavily customized so we clobber the whole file. 
   - paths: [