chore: update codeowners and remove secrets scan workflow

Author: harshitha-cstk

.github/workflows/secrets-scan.yml

@@ -1 +1,11 @@
-* @contentstack/security-admin
+* @contentstack/devex-pr-reviewers
+
+.github/workflows/sca-scan.yml @contentstack/security-admin
+
+.github/workflows/codeql-anaylsis.yml @contentstack/security-admin
+
+**/.snyk @contentstack/security-admin
+
+.github/workflows/policy-scan.yml @contentstack/security-admin
+
+.github/workflows/issues-jira.yml @contentstack/security-admin