Fix fileMatch for commodore-helm manager

We need to anchor the beginning of `fileMatch` commodore-helm regex so
that we don't accidentally match any files in golden tests which match
`class/[^.]+.ya?ml$`.

Unfortunately, writing a test for this is tricky because we're
configuring Renovate internals which we can't easily exercise in our
test cases.

src/commodore-helm/__snapshots__/index.spec.ts.snap

@@ -21,6 +21,27 @@ exports[`manager/commodore-helm/index extractAllPackageFiles() extracts new and
 ]
 `;
 
+exports[`manager/commodore-helm/index extractAllPackageFiles() extracts new and old standard Helm dependencies in the same file in the presence of golden tests 1`] = `
+[
+  {
+    "currentValue": "1.2.3",
+    "depName": "chart-1",
+    "groupName": "component-name",
+    "registryUrls": [
+      "https://charts.example.com/",
+    ],
+  },
+  {
+    "currentValue": "4.5.6",
+    "depName": "chart-2",
+    "groupName": "component-name",
+    "registryUrls": [
+      "https://charts2.example.com/",
+    ],
+  },
+]
+`;
+
 exports[`manager/commodore-helm/index extractAllPackageFiles() extracts old standard Helm dependencies 1`] = `
 [
   {

src/commodore-helm/index.ts

@@ -28,7 +28,7 @@ interface KapitanHelmDependency extends KapitanDependency {
 
 export const defaultConfig = {
   // match all class files of the component
-  fileMatch: ['class/[^.]+.ya?ml$'],
+  fileMatch: ['^class/[^.]+.ya?ml$'],
 };
 
 export const supportedDatasources = [HelmDatasource.id];