Update module flags documentation for Min.

[jbramley]

Summary

This updates the documentation to match the implementation. Warning and
Min interact in the same way as Warning and Max.

[jbramley]

+ other reviewers from D123493, where this behaviour was introduced.

[tejohnson]

lgtm

llvm/docs/LangRef.rst

.. list-table::
    * - 1
      - **Error**
            Emits an error if two values disagree, otherwise the resulting value
            is that of the operands.
 
    * - 2
      - **Warning**
            Emits a warning if two values disagree. The result value will be the
-           operand for the flag from the first module being linked, or the max
-           if the other module uses **Max** (in which case the resulting flag
-           will be **Max**).
+           operand for the flag from the first module being linked, unless the
+           other module uses **Min** or **Max**, in which case the result will
+           be **Min** (with the min value) or **Max** (with the max value),
+           respectively.
 
    * - 3
      - **Require**
            Adds a requirement that another module flag be present and have a
            specified value after linking is performed. The value must be a
            metadata pair, where the first element of the pair is the ID of the
            module flag to be restricted, and the second element of the pair is
            the value the module flag should be restricted to. This behavior can