spell out acronym

Author: devalog

fern/products/sdks/overview/csharp/version-compatibility.mdx

@@ -13,7 +13,7 @@ Because these SDKs are built with modern C# features, you'll need the following
 
 Fern .NET SDKs support [all officially supported .NET versions](https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-framework), except for net35.
 
-| Framework | TFM |
+| Framework | Target Framework Moniker (TFM) |
 |--------|----------|
 | .NET 9 | net9.0 |
 | .NET 8 | net8.0 |