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

[Erich Keane via cfe-commits]

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@@ -138,7 +120,7 @@ Let's see a "hello world" example that uses modules.
     return 0;
   }
 
-Then we type:
+From the command line, enter:
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erichkeane wrote:

Then, on the command line, invoke clang like:

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