Remove 5.8.x and 6.2.x dependabot configuration

Closes gh-16268

.github/dependabot.yml

@@ -4,56 +4,6 @@ registries:
     type: maven-repository
     url: https://repo.spring.io/milestone
 updates:
-  - package-ecosystem: gradle
-    target-branch: 5.8.x
-    directory: /
-    schedule:
-      interval: daily
-      time: '03:00'
-      timezone: Etc/UTC
-    labels:
-      - 'type: dependency-upgrade'
-    registries:
-      - spring-milestones
-    ignore:
-      - dependency-name: com.nimbusds:nimbus-jose-jwt
-      - dependency-name: org.python:jython
-      - dependency-name: org.apache.directory.server:*
-      - dependency-name: org.junit:junit-bom
-        update-types:
-          - version-update:semver-major
-      - dependency-name: org.mockito:mockito-bom
-        update-types:
-          - version-update:semver-major
-      - dependency-name: '*'
-        update-types:
-          - version-update:semver-major
-          - version-update:semver-minor
-  - package-ecosystem: gradle
-    target-branch: 6.2.x
-    directory: /
-    schedule:
-      interval: daily
-      time: '03:00'
-      timezone: Etc/UTC
-    labels:
-      - 'type: dependency-upgrade'
-    registries:
-      - spring-milestones
-    ignore:
-      - dependency-name: com.nimbusds:nimbus-jose-jwt
-      - dependency-name: org.python:jython
-      - dependency-name: org.apache.directory.server:*
-      - dependency-name: org.junit:junit-bom
-        update-types:
-          - version-update:semver-major
-      - dependency-name: org.mockito:mockito-bom
-        update-types:
-          - version-update:semver-major
-      - dependency-name: '*'
-        update-types:
-          - version-update:semver-major
-          - version-update:semver-minor
   - package-ecosystem: gradle
     target-branch: 6.3.x
     directory: /
@@ -108,26 +58,6 @@ updates:
         update-types:
           - version-update:semver-major
 
-  - package-ecosystem: github-actions
-    target-branch: 5.8.x
-    directory: /
-    schedule:
-      interval: weekly
-    labels:
-      - 'type: task'
-      - 'in: build'
-    ignore:
-      - dependency-name: sjohnr/*
-  - package-ecosystem: github-actions
-    target-branch: 6.2.x
-    directory: /
-    schedule:
-      interval: weekly
-    labels:
-      - 'type: task'
-      - 'in: build'
-    ignore:
-      - dependency-name: sjohnr/*
   - package-ecosystem: github-actions
     target-branch: 6.3.x
     directory: /
@@ -184,19 +114,3 @@ updates:
     labels:
       - 'type: task'
       - 'in: build'
-  - package-ecosystem: npm
-    target-branch: 6.2.x
-    directory: /docs
-    schedule:
-      interval: weekly
-    labels:
-      - 'type: task'
-      - 'in: build'
-  - package-ecosystem: npm
-    target-branch: 5.8.x
-    directory: /docs
-    schedule:
-      interval: weekly
-    labels:
-      - 'type: task'
-      - 'in: build'