Update dependabot.yml

Author: Achim Schneider

.github/dependabot.yml

@@ -7,15 +7,19 @@ updates:
       interval: daily
       time: '03:00'
       timezone: Europe/Berlin
+    open-pull-requests-limit: 10
   - package-ecosystem: npm
     directory: '/'
     schedule:
       interval: 'daily'
+    open-pull-requests-limit: 10
   - package-ecosystem: cargo
     directory: '/'
     schedule:
       interval: 'daily'
+    open-pull-requests-limit: 10
   - package-ecosystem: docker
     directory: '/'
     schedule:
       interval: 'daily'
+    open-pull-requests-limit: 10