Set open-pull-requests-limit=20 for each package-ecosystem

Author: rwinch

.github/dependabot.yml

@@ -14,6 +14,7 @@ updates:
       interval: "daily"
       time: "03:00"
       timezone: "Etc/UTC"
+    open-pull-requests-limit: 20
     labels: [ "type: dependency-upgrade" ]
     registries:
       - "spring-milestones"
@@ -32,6 +33,7 @@ updates:
       interval: "daily"
       time: "03:00"
       timezone: "Etc/UTC"
+    open-pull-requests-limit: 20
     labels: [ "type: dependency-upgrade" ]
     registries:
       - "spring-milestones"
@@ -50,6 +52,7 @@ updates:
       interval: "daily"
       time: "03:00"
       timezone: "Etc/UTC"
+    open-pull-requests-limit: 20
     labels: [ "type: dependency-upgrade" ]
     ignore:
       - dependency-name: "org.junit:junit-bom"
@@ -66,24 +69,29 @@ updates:
     directory: "/"
     schedule:
       interval: weekly
+    open-pull-requests-limit: 20
   - package-ecosystem: github-actions
     target-branch: "3.5.x"
     directory: "/"
     schedule:
       interval: weekly
+    open-pull-requests-limit: 20
   - package-ecosystem: github-actions
     target-branch: "3.4.x"
     directory: "/"
     schedule:
       interval: weekly
+    open-pull-requests-limit: 20
   - package-ecosystem: github-actions
     target-branch: "docs-build"
     directory: "/"
     schedule:
       interval: weekly
+    open-pull-requests-limit: 20
 
   - package-ecosystem: npm
     target-branch: docs-build
     directory: /
     schedule:
       interval: weekly
+    open-pull-requests-limit: 20