C#: Update the description of the telemetry queries.

Author: michaelnebel

csharp/ql/src/Telemetry/SupportedExternalSinks.ql

@@ -1,6 +1,6 @@
 /**
  * @name Supported sinks in external libraries
- * @description A list of 3rd party APIs detected as sinks. Excludes test and generated code.
+ * @description A list of 3rd party APIs detected as sinks. Excludes APIs exposed by test libraries.
  * @kind metric
  * @tags summary
  * @id csharp/telemetry/supported-external-api-sinks

csharp/ql/src/Telemetry/SupportedExternalSources.ql

@@ -1,6 +1,6 @@
 /**
  * @name Supported sources in external libraries
- * @description A list of 3rd party APIs detected as sources. Excludes test and generated code.
+ * @description A list of 3rd party APIs detected as sources. Excludes APIs exposed by test libraries.
  * @kind metric
  * @tags summary
  * @id csharp/telemetry/supported-external-api-sources

csharp/ql/src/Telemetry/SupportedExternalTaint.ql

@@ -1,6 +1,6 @@
 /**
  * @name Supported flow steps in external libraries
- * @description A list of 3rd party APIs detected as flow steps. Excludes test and generated code.
+ * @description A list of 3rd party APIs detected as flow steps. Excludes APIs exposed by test libraries.
  * @kind metric
  * @tags summary
  * @id csharp/telemetry/supported-external-api-taint

csharp/ql/src/Telemetry/UnsupportedExternalAPIs.ql

@@ -1,6 +1,6 @@
 /**
  * @name Usage of unsupported APIs coming from external libraries
- * @description A list of 3rd party APIs used in the codebase. Excludes test and generated code.
+ * @description A list of 3rd party APIs used in the codebase. Excludes APIs exposed by test libraries.
  * @kind metric
  * @tags summary
  * @id csharp/telemetry/unsupported-external-api