ci: move from dependabot reviewers to CODEOWNERS (#491)

* ci: move from dependabot reviewers to CODEOWNERS

Author: oakrizan

.github/CODEOWNERS

@@ -0,0 +1,5 @@
+# Default owner
+* @elastic/apm-agent-python
+
+# Sub-directories/files ownership
+/.github/workflows @elastic/observablt-ci

.github/dependabot.yml

@@ -10,8 +10,6 @@ updates:
       interval: "weekly"
       day: "sunday"
       time: "22:00"
-    reviewers:
-      - "elastic/apm-agent-python"
 
 
   # Enable version updates for Docker
@@ -22,13 +20,9 @@ updates:
       interval: "weekly"
       day: "sunday"
       time: "22:00"
-    reviewers:
-      - "elastic/apm-agent-python"
 
   - package-ecosystem: "github-actions"
     directory: "/"
-    reviewers:
-      - "elastic/observablt-ci"
     schedule:
       interval: "weekly"
       day: "sunday"