Remove braces while serializing {OriginalFormat}

[Reiley Yang (reyang)]

Similar to #2071.

The following code would cause a key-value pair in the property bag with the key equals to {OriginalFormat}.

            Application Insights Telemetry: 
            {
              "name":"AppTraces",
              "time":"2021-04-22T22:41:50.4529345Z",
              "iKey":"--YourAIKeyHere--",
              "tags":{
                "ai.application.ver":"1.0.0.0",
                "ai.cloud.roleInstance":"-------------",
                "ai.internal.sdkVersion":"il:2.17.0-146",
                "ai.internal.nodeName":"----------"
              },
              "data":{
                "baseType":"MessageData",
                "baseData":{
                  "ver":2,
                  "message":"Test application is starting",
                  "severityLevel":"Information",
                  "properties":{
                    "AspNetCoreEnvironment":"Development",
                    "DeveloperMode":"true",
                    "CategoryName":"AppInsightsScopeTest.TestApplication",
                                            "{OriginalFormat}":"TestScope {ScopeColumn1} and {ScopeColumn2}",    <----- !!! THIS IS WHAT PROBABLY BREAKS KUSTO !!!
                    "OriginalFormat":"Test application is starting",
                    "ScopeColumn2":"5678",
                    "ScopeColumn1":"1234"
                  }
                }
              }
            }

[Timothy Mothra (TimothyMothra)]

LGTM. Should we add any unit tests?

[Reiley Yang (reyang)]

LGTM. Should we add any unit tests?

I've added unit tests.