codeowners: only care for the workflows subfolder (#17502)

Author: v1v

.github/CODEOWNERS

@@ -2,4 +2,4 @@
 * @elastic/obs-ds-intake-services
 
 # Sub-directories/files ownership
-/.github @elastic/obs-ds-intake-services @elastic/observablt-ci
+/.github/workflows @elastic/obs-ds-intake-services @elastic/observablt-ci