Fix readme.go.md in compute RP (#14631)

* add the missing $

* remove one useless directive

* fix

* remove the hack for track 2 and add comments for reasons

* add one of the directive back to readme.go.md

* add some comment to explain this more

* fix

Author: ArcturusZhang

specification/compute/resource-manager/readme.go.md

@@ -2,13 +2,14 @@
 
 These settings apply only when `--go` is specified on the command line.
 
-```yaml $(go) && !(track2)
+```yaml $(go) && !$(track2)
 go:
   license-header: MICROSOFT_MIT_NO_VERSION
   clear-output-folder: true
 
 directive:
-    # dynamically add a DummyOrchestrationServiceName value to the enum 
+    # dynamically add a DummyOrchestrationServiceName value to the enum and then remove it from the generated code to avoid the generator generates the code by hard-coding the single-entry enum value
+    # this directive adds a DummyOrchestrationServiceName to the enum type
   - from: compute.json
     where: $..enum
     transform: >-
@@ -17,14 +18,15 @@ directive:
       }
       return $;
 
+    # this directive removes the DummyOrchestrationServiceName from the generated code, so that we still have only one enum entry in this enum type.
   - from: source-file-go
     where: $ 
     transform: >-
       return $.
-        replace(/\/\/ DummyOrchestrationServiceName .../g,'').
-        replace(/DummyOrchestrationServiceName OrchestrationServiceNames = "DummyOrchestrationServiceName"\n/g,'').
-        replace(/,DummyOrchestrationServiceName/,'').
-        replace(/, 'DummyOrchestrationServiceName'/,'');
+        replace(/\/\/ (OrchestrationServiceNames)?DummyOrchestrationServiceName .../g,'').
+        replace(/(OrchestrationServiceNames)?DummyOrchestrationServiceName OrchestrationServiceNames = "DummyOrchestrationServiceName"\n/g,'').
+        replace(/,(OrchestrationServiceNames)?DummyOrchestrationServiceName/,'').
+        replace(/, '(OrchestrationServiceNames)?DummyOrchestrationServiceName'/,'');
 ```
 
 ``` yaml $(go) && $(track2)
@@ -35,6 +37,7 @@ output-folder: $(go-sdk-folder)/$(module-name)
 azure-arm: true
 
 directive:
+  # we do not need to hack to add a dummy enum entry in track 2, because track 2 generator will generate the enum type even if it only has on entry 
   - from: disk.json
     where: "$.definitions.PurchasePlan"
     transform: >