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

[via cfe-commits]

================
@@ -633,36 +631,36 @@ example:
                                   // module M's interface, so is discarded
   int c = use_h<int>();           // OK
 
-In the above example, the function definition of ``N::g`` is elided from the Reduced
-BMI of ``M.cppm``. Then the use of ``use_g<int>`` in ``M-impl.cpp`` fails
-to instantiate. For such issues, users can add references to ``N::g`` in the module purview
-of ``M.cppm`` to make sure it is reachable, e.g., ``using N::g;``.
-
-We think the Reduced BMI is the correct direction. But given it is a drastic change,
-we'd like to make it experimental first to avoid breaking existing users. The roadmap
-of Reduced BMI may be:
-
-1. ``-fexperimental-modules-reduced-bmi`` is opt in for 1~2 releases. The period depends
-on testing feedbacks.
-2. We would announce Reduced BMI is not experimental and introduce ``-fmodules-reduced-bmi``.
-and suggest users to enable this mode. This may takes 1~2 releases too.
-3. Finally we will enable this by default. When that time comes, the term BMI will refer to
-the reduced BMI today and the Full BMI will only be meaningful to build systems which
-loves to support two phase compilations.
+In the above example, the function definition of ``N::g`` is elided from the
+Reduced BMI of ``M.cppm``. Then the use of ``use_g<int>`` in ``M-impl.cpp``
+fails to instantiate. For such issues, users can add references to ``N::g`` in
+the module purview of ``M.cppm`` to ensure it is reachable, e.g.,
+``using N::g;``.
+
+Long-term, Clang is likely to make Reduced BMIs the default rather than Full
----------------
cor3ntin wrote:

Support for reduced BMI is still experimental but it might become the default in the future.

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