Disable Dependabot version updates

This allows security updates to still get created.

This behavior is documented at
https://docs.github.com/en/code-security/dependabot/dependabot-security-updates/configuring-dependabot-security-updates#overriding-the-default-behavior-with-a-configuration-file

.github/dependabot.yml

@@ -4,7 +4,8 @@ updates:
     directory: "/"
     schedule:
       interval: daily
-    open-pull-requests-limit: 20
+    # disable version updates
+    open-pull-requests-limit: 0
     assignees:
       - "Pyker"
     ignore: