nit: Fix comment to be up-to-date (open-telemetry#1510)

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

trace.go

@@ -22,7 +22,7 @@ import (
 // Tracer creates a named tracer that implements Tracer interface.
 // If the name is an empty string then provider uses default name.
 //
-// This is short for TracerProvider().Tracer(name)
+// This is short for GetTracerProvider().Tracer(name)
 func Tracer(name string) trace.Tracer {
  return GetTracerProvider().Tracer(name)
 }