Add 0.20 dependabot config; remove 0.15

Signed-off-by: Tom Pantelis <tompantelis@gmail.com>

Author: tpantelis

.github/dependabot.yml

@@ -11,7 +11,7 @@ updates:
           - "*"
   - package-ecosystem: github-actions
     directory: /
-    target-branch: release-0.15
+    target-branch: release-0.16
     schedule:
       interval: monthly
     groups:
@@ -20,7 +20,7 @@ updates:
           - "*"
   - package-ecosystem: github-actions
     directory: /
-    target-branch: release-0.16
+    target-branch: release-0.17
     schedule:
       interval: monthly
     groups:
@@ -29,7 +29,7 @@ updates:
           - "*"
   - package-ecosystem: github-actions
     directory: /
-    target-branch: release-0.17
+    target-branch: release-0.18
     schedule:
       interval: monthly
     groups:
@@ -38,7 +38,16 @@ updates:
           - "*"
   - package-ecosystem: github-actions
     directory: /
-    target-branch: release-0.18
+    target-branch: release-0.19
+    schedule:
+      interval: monthly
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+  - package-ecosystem: github-actions
+    directory: /
+    target-branch: release-0.20
     schedule:
       interval: monthly
     groups: