Fix typo in link to regression in 1.32.0 upgrade notes

UPGRADE.rst

@@ -91,7 +91,7 @@ Upgrading to v1.32.0
 Regression causing connected Prometheus instances to become overwhelmed
 -----------------------------------------------------------------------
 
-This release introduces `a regression <https://githubcom/matrix-org/synapse/issues/9853>`_
+This release introduces `a regression <https://github.com/matrix-org/synapse/issues/9853>`_
 that can overwhelm connected Prometheus instances. This issue was not present in
 Synapse v1.32.0rc1. It is recommended not to update to this release. If you have
 upgraded to v1.32.0 already, please downgrade to v1.31.0. This issue will be