build(deps): bump helm-diff to v3.15.13 (#2788)

* build(deps): bump helm-diff to v3.15.13

Update helm-diff plugin version from v3.15.12 to v3.15.13 across
Dockerfiles, recommended version constant, CI matrix, and
integration test default.

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix(ci): add golden files for helm-diff >= 3.15.13

helm-diff v3.15.13 omits null/empty labels and annotations keys from
diffs (databus23/helm-diff#1068), which broke the suppress-output-line-
regex integration test: the ValidatingWebhookConfiguration manifest no
longer renders a bare 'annotations:' key under metadata.

Add new golden files suffixed -after-helm-diff-3.15.13 (helm3, helm4,
live variants) and select them via version_ge in the test case, keeping
the existing 3.11.0 and pre-3.11.0 goldens for older plugin versions.

Signed-off-by: yxxhero <aiopsclub@163.com>

* refactor(test): drop legacy helm-diff golden files

CI only exercises the recommended helm-diff version, so replace the
version-suffixed golden files (-after-helm-diff-3.11.0,
-after-helm-diff-3.15.13) with a single set of base golden files
(diff, diff-live, diff-helm4, diff-live-helm4) containing the
v3.15.13 output, and remove the now-dead version gating.

Also drop the 'install semver' CI step, whose only consumer was the
removed gating.

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix(test): remove helm-diff version gating from golden file selection

The previous commit deleted the version-suffixed golden files but the
selection gating was accidentally left behind, making the test reference
non-existent files for helm-diff >= 3.15.13.

Signed-off-by: yxxhero <aiopsclub@163.com>

---------

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/app/init.go

@@ -19,7 +19,7 @@ import (
 
 const (
 	HelmRequiredVersion            = "v3.18.6" // Minimum required version (supports Helm 3.x and 4.x)
-	HelmDiffRecommendedVersion     = "v3.15.12"
+	HelmDiffRecommendedVersion     = "v3.15.13"
 	HelmRecommendedVersion         = "v4.3.0" // Recommended Helm 4 version
 	HelmSecretsRecommendedVersion  = "v4.7.4" // v4.7.0+ works with both Helm 3 (single plugin) and Helm 4 (split plugin architecture)
 	HelmGitRecommendedVersion      = "v1.3.0"