fix(init): rename 'Custom Metrics' feature label to 'Metrics'

The metrics feature was labeled 'Custom Metrics' in the feature selection
prompt, which doesn't match Sentry's standard terminology. Rename to
'Metrics' for consistency.

Closes getsentry/cli-init-api#59

Author: MathurAditya724

src/lib/init/clack-utils.ts

@@ -43,7 +43,7 @@ const FEATURE_INFO: Record<string, { label: string; hint: string }> = {
     hint: "Code-level performance insights",
   },
   logs: { label: "Logging", hint: "Structured log ingestion" },
-  metrics: { label: "Custom Metrics", hint: "Track custom business metrics" },
+  metrics: { label: "Metrics", hint: "Track business metrics" },
   sourceMaps: {
     label: "Source Maps",
     hint: "See original source code in production errors",