Set the chart's placeholder version to 0.6.0

Cosmetic: make helm-package passes --version and --app-version from the tag,
so these fields decide nothing about what is published. They are kept in
step so the tree does not state an older number than the release it heads
for.

Claude-Session: https://claude.ai/code/session_016mBLURvJoMuUEr9cB2RpUN

charts/terdut-operator/Chart.yaml

@@ -6,8 +6,8 @@ type: application
 # These fields decide nothing: `make helm-package` passes --version and
 # --app-version from the release tag (same reasoning as terdut-server's own
 # chart). They're for whoever reads the tree before a tag exists.
-version: 0.5.0
-appVersion: "v0.5.0"
+version: 0.6.0
+appVersion: "v0.6.0"
 
 keywords:
   - kubernetes