feat: Update description on allowed_locations in LocationPolicy field

---
feat: Add UpdateJob API to update the job spec, only task_count is supported now

docs: updated comments
PiperOrigin-RevId: 631869976

google/cloud/batch/v1alpha/batch.proto

@@ -75,6 +75,15 @@ service BatchService {
     };
   }
 
+  // Update a Job.
+  rpc UpdateJob(UpdateJobRequest) returns (Job) {
+    option (google.api.http) = {
+      patch: "/v1alpha/{job.name=projects/*/locations/*/jobs/*}"
+      body: "job"
+    };
+    option (google.api.method_signature) = "job,update_mask";
+  }
+
   // List all Jobs for a project within a region.
   rpc ListJobs(ListJobsRequest) returns (ListJobsResponse) {
     option (google.api.http) = {
@@ -224,6 +233,38 @@ message DeleteJobRequest {
   string request_id = 4 [(google.api.field_behavior) = OPTIONAL];
 }
 
+// UpdateJob Request.
+message UpdateJobRequest {
+  // Required. The Job to update.
+  // Only fields specified in `update_mask` are updated.
+  Job job = 1 [(google.api.field_behavior) = REQUIRED];
+
+  // Required. Mask of fields to update.
+  //
+  // UpdateJob request now only supports update on `task_count` field in a job's
+  // first task group. Other fields will be ignored.
+  google.protobuf.FieldMask update_mask = 2
+      [(google.api.field_behavior) = REQUIRED];
+
+  // Optional. An optional request ID to identify requests. Specify a unique
+  // request ID so that if you must retry your request, the server will know to
+  // ignore the request if it has already been completed. The server will
+  // guarantee that for at least 60 minutes after the first request.
+  //
+  // For example, consider a situation where you make an initial request and
+  // the request times out. If you make the request again with the same request
+  // ID, the server can check if original operation with the same request ID
+  // was received, and if so, will ignore the second request. This prevents
+  // clients from accidentally creating duplicate commitments.
+  //
+  // The request ID must be a valid UUID with the exception that zero UUID is
+  // not supported (00000000-0000-0000-0000-000000000000).
+  string request_id = 3 [
+    (google.api.field_info).format = UUID4,
+    (google.api.field_behavior) = OPTIONAL
+  ];
+}
+
 // ListJob Request.
 message ListJobsRequest {
   // Parent path.

google/cloud/batch/v1alpha/job.proto

@@ -317,11 +317,11 @@ message AllocationPolicy {
     // ["zones/us-central1-a", "zones/us-central1-c"] only allow VMs
     // in zones us-central1-a and us-central1-c.
     //
-    // All locations end up in different regions would cause errors.
+    // Mixing locations from different regions would cause errors.
     // For example,
     // ["regions/us-central1", "zones/us-central1-a", "zones/us-central1-b",
-    // "zones/us-west1-a"] contains 2 regions "us-central1" and
-    // "us-west1". An error is expected in this case.
+    // "zones/us-west1-a"] contains locations from two distinct regions:
+    // us-central1 and us-west1. This combination will trigger an error.
     repeated string allowed_locations = 1;
 
     // A list of denied location names.