remove wrong read-only from RetentionInDays property (#15247)

* remove readonly from RetentionInDays

* fix

* fix

* fix

Author: tofriedl

specification/applicationinsights/resource-manager/Microsoft.Insights/stable/2020-02-02/components_API.json

@@ -572,8 +572,7 @@
         },
         "RetentionInDays": {
           "type": "integer",
-          "description": "Retention period in days.",
-          "readOnly": true
+          "description": "Retention period in days."
         },
         "DisableIpMasking": {
           "type": "boolean",

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

@@ -32,5 +32,5 @@ These settings apply only when `--tag=package-2020-02-02 --go` is specified on h
 Please also specify `--go-sdk-folder=<path to the root directory of your azure-sdk-for-go clone>`.
 
 ``` yaml $(tag) == 'package-2020-02-02' && $(go)
-output-folder: $(go-sdk-folder)/services/preview/appinsights/mgmt/2020-02-02-preview/$(namespace)
+output-folder: $(go-sdk-folder)/services/appinsights/mgmt/2020-02-02/$(namespace)
 ```

specification/applicationinsights/resource-manager/readme.md

@@ -374,7 +374,6 @@ input-file:
 - Microsoft.Insights/stable/2015-05-01/workbooks_API.json
 - Microsoft.Insights/stable/2015-05-01/myworkbooks_API.json
 - Microsoft.Insights/stable/2020-02-02/components_API.json
-- Microsoft.Insights/preview/2020-03-01-preview/componentLinkedStorageAccounts_API.json
 ```
 
 ### Tag: package-2019-10-17-preview