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

[via cfe-commits]

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@@ -95,22 +76,23 @@ In this document, we use the following umbrella terms:
 * A ``module interface unit`` refers to either a ``primary module interface unit``
   or a ``module interface partition unit``.
 
-* An ``importable module unit`` refers to either a ``module interface unit``
-  or a ``internal module partition unit``.
+* An ``importable module unit`` refers to either a ``module interface unit`` or
+  an ``internal module partition unit``.
 
 * A ``module partition unit`` refers to either a ``module interface partition unit``
-  or a ``internal module partition unit``.
+  or an ``internal module partition unit``.
 
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cor3ntin wrote:

https://learn.microsoft.com/en-us/cpp/cpp/modules-cpp?view=msvc-170

S/internal/implementation 


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