Remove Dependabot entries for retired branch 4.3.x

Author: spring-builds

.github/dependabot.yml

@@ -5,17 +5,6 @@ updates:
     target-branch: "main"
     schedule:
       interval: "weekly"
-  - package-ecosystem: maven
-    directory: /
-    schedule:
-      interval: daily
-    target-branch: 4.3.x
-    ignore:
-      # only upgrade patch versions for maintenance branch
-      - dependency-name: "*"
-        update-types:
-          - version-update:semver-major
-          - version-update:semver-minor
   - package-ecosystem: maven
     directory: /
     schedule:
@@ -37,8 +26,3 @@ updates:
     directory: /docs
     schedule:
       interval: weekly
-  - package-ecosystem: npm
-    target-branch: 4.3.x
-    directory: /docs
-    schedule:
-      interval: weekly