[clang] Revise the modules document for clarity (PR #90237)

[Erich Keane via cfe-commits]

================
@@ -875,11 +872,11 @@ The pattern for ABI breaking style is similar with export extern-C++ style.
   }
   #endif
 
-(And add `EXPORT` and conditional include to the headers as suggested in the export
-extern-C++ style section)
+(And add `EXPORT` and conditional include to the headers as suggested in the
+export extern-C++ style section.)
 
-Remember that the ABI get changed and we need to compile our source files into the
-new ABI format. This is the job of the additional part of the interface unit:
+The ABI with modules is different and so we need to compile the source files
----------------
erichkeane wrote:

```suggestion
The ABI with modules is different and thus we need to compile the source files
```

https://github.com/llvm/llvm-project/pull/90237