dotnet performance clarify GetSpan (#5078)

Co-authored-by: Isabel <76437239+imatwawana@users.noreply.github.com>
Co-authored-by: Matt Johnson-Pint <mattjohnsonpint@gmail.com>
Co-authored-by: Bruno Garcia <bruno@brunogarcia.com>

src/includes/performance/retrieve-transaction/dotnet.mdx

@@ -1,6 +1,6 @@
 ## Retrieve a Transaction
 
-In cases where you want to attach Spans to an already ongoing Transaction you can use `Sentry#GetSpan`. This method will return a `SentryTransaction` in case there is a running Transaction or a `Span` in case there is already a running Span, otherwise it returns `null`.
+In cases where you want to attach Spans to an already ongoing Transaction you can use `SentrySdk.GetSpan()`. If there is a running Transaction or Span currently on the scope, this method will return a `SentryTransaction` or `Span`; otherwise, it returns `null`.
 
 ```csharp
 using Sentry;