Merge pull request #639 from fluxcd/drift-detection-heading

spec: change drift detection heading

Author: hiddeco

docs/spec/v2beta1/helmreleases.md

@@ -1270,7 +1270,7 @@ spec:
     crds: CreateReplace
 ```
 
-### Drift detection
+## Drift detection
 
 **Note:** This feature is experimental and can be enabled by setting `--feature-gates=DetectDrift=true`.