fix: remove trailing slashes from intersphinx (#4886)

Some trailing slashes will redirect to remove the duplicate slashes,
save some traffic.

Resolves build-time logged lines that look like:

    intersphinx inventory has moved: ...

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

Author: miketheman

peps/conf.py

@@ -69,17 +69,17 @@
 
 # Intersphinx configuration (keep this in alphabetical order)
 intersphinx_mapping = {
-    "devguide": ("https://devguide.python.org/", None),
-    "mypy": ("https://mypy.readthedocs.io/en/latest/", None),
-    "packaging": ("https://packaging.python.org/en/latest/", None),
-    "py3.11": ("https://docs.python.org/3.11/", None),
-    "py3.12": ("https://docs.python.org/3.12/", None),
-    "py3.13": ("https://docs.python.org/3.13/", None),
-    "py3.14": ("https://docs.python.org/3.14/", None),
-    "py3.15": ("https://docs.python.org/3.15/", None),
-    "python": ("https://docs.python.org/3/", None),
-    "trio": ("https://trio.readthedocs.io/en/latest/", None),
-    "typing": ("https://typing.python.org/en/latest/", None),
+    "devguide": ("https://devguide.python.org", None),
+    "mypy": ("https://mypy.readthedocs.io/en/latest", None),
+    "packaging": ("https://packaging.python.org/en/latest", None),
+    "py3.11": ("https://docs.python.org/3.11", None),
+    "py3.12": ("https://docs.python.org/3.12", None),
+    "py3.13": ("https://docs.python.org/3.13", None),
+    "py3.14": ("https://docs.python.org/3.14", None),
+    "py3.15": ("https://docs.python.org/3.15", None),
+    "python": ("https://docs.python.org/3", None),
+    "trio": ("https://trio.readthedocs.io/en/latest", None),
+    "typing": ("https://typing.python.org/en/latest", None),
 }
 intersphinx_disabled_reftypes = []