Remove resource exhasted scopes for namespace shard and execution (#654)

**Why?**

After internal discussions, we decided not to add these new scopes and
rely on the cause enum for more granular resolution.

**Breaking changes**

Yes, but the version of the API that includes these enum values has
never been released.

Author: bergundy

buf.yaml

@@ -13,6 +13,7 @@ breaking:
     - WIRE_JSON
   ignore:
     - google
+    - temporal/api/enums/v1/failed_cause.proto
 lint:
   use:
     - DEFAULT

temporal/api/enums/v1/failed_cause.proto

@@ -131,9 +131,5 @@ enum ResourceExhaustedScope {
     RESOURCE_EXHAUSTED_SCOPE_NAMESPACE = 1;
     // Exhausted resource is a namespace-level resource.
     RESOURCE_EXHAUSTED_SCOPE_SYSTEM = 2;
-    // Exhausted resource is a namespace-level, shard-level resource.
-    RESOURCE_EXHAUSTED_SCOPE_NAMESPACE_SHARD = 3;
-    // Exhausted resource is an execution-level resource.
-    RESOURCE_EXHAUSTED_SCOPE_EXECUTION = 4;
 }