Update metrics sample with newer Prometheus suggestions

[cretz]

Describe the solution you'd like

When https://github.com/temporalio/sdk-go/pull/756 is released, apply this:

diff --git a/metrics/worker/main.go b/metrics/worker/main.go
index c1dc254..e3dde80 100644
--- a/metrics/worker/main.go
+++ b/metrics/worker/main.go
@@ -53,35 +53,12 @@ func newPrometheusScope(c prometheus.Configuration) tally.Scope {
        scopeOpts := tally.ScopeOptions{
                CachedReporter:  reporter,
                Separator:       prometheus.DefaultSeparator,
-               SanitizeOptions: &sanitizeOptions,
+               SanitizeOptions: &sdktally.PrometheusSanitizeOptions,
                Prefix:          "temporal_samples",
        }
        scope, _ := tally.NewRootScope(scopeOpts, time.Second)
+       scope = sdktally.NewPrometheusNamingScope(scope)

        log.Println("prometheus metrics scope created")
        return scope
 }
-
-// tally sanitizer options that satisfy Prometheus restrictions.
-// This will rename metrics at the tally emission level, so metrics name we
-// use maybe different from what gets emitted. In the current implementation
-// it will replace - and . with _
-var (
-       safeCharacters = []rune{'_'}
-
-       sanitizeOptions = tally.SanitizeOptions{
-               NameCharacters: tally.ValidCharacters{
-                       Ranges:     tally.AlphanumericRange,
-                       Characters: safeCharacters,
-               },
-               KeyCharacters: tally.ValidCharacters{
-                       Ranges:     tally.AlphanumericRange,
-                       Characters: safeCharacters,
-               },
-               ValueCharacters: tally.ValidCharacters{
-                       Ranges:     tally.AlphanumericRange,
-                       Characters: safeCharacters,
-               },
-               ReplacementCharacter: tally.DefaultReplacementCharacter,
-       }
-)