dependabot: run daily

Running only weekly just adds latency until PRs are created with no apparent
benefit. Multiple releases within a week for the same module happen rarely, so
it doesn't reduce the number of PRs.

.github/dependabot.yml

@@ -3,6 +3,5 @@ updates:
 - package-ecosystem: gomod
   directory: "/"
   schedule:
-    interval: weekly
-    time: '10:00'
+    interval: daily
   open-pull-requests-limit: 10