fix(dependabot): disable update PR till e2e coverage is completed (#959)

## Changes

- prevents opening new minor dep update PRs by dependabot until we feel
good about the e2e coverage and it's running on Dev (we'll still get the
security updates, this only applies to the deluge of minor updates we
get)

Closes #835 

## How to test this PR

1. After this is merged, do you see less dependabot updates?

.github/dependabot.yml

@@ -13,3 +13,7 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
+    # Once we feel comfortable with e2e test coverage and it's running on dev, we can re-enable this
+    # see: https://github.com/cfpb/sbl-frontend/issues/835
+    # see also: https://github.com/cfpb/sbl-frontend/issues/957
+    open-pull-requests-limit: 0