[gcc r13-1188] doc: Document module language-linkage supported

[Nathan Sidwell <nathan@gcc.gnu.org>]

https://gcc.gnu.org/g:f1fcd6e3ad911945bc3c24a3a5c7ea99b910121e

commit r13-1188-gf1fcd6e3ad911945bc3c24a3a5c7ea99b910121e
Author: Nathan Sidwell <nathan@acm.org>
Date:   Tue Jun 21 06:23:11 2022 -0700

    doc: Document module language-linkage supported
    
    I missed we documented this as unimplemented, when I implemented it.
    
            gcc/
            * doc/invoke.texi (C++ Modules): Remove language-linkage
            as missing feature.

Diff:
---
 gcc/doc/invoke.texi | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 50f57877477..81d13f4e78e 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -34639,13 +34639,6 @@ Papers p1815 (@uref{https://wg21.link/p1815}) and p2003
 exported region may reference (for instance, the entities an exported
 template definition may reference).  These are not fully implemented.
 
-@item Language-linkage module attachment
-Declarations with explicit language linkage (@code{extern "C"} or
-@code{extern "C++"}) are attached to the global module, even when in
-the purview of a named module.  This is not implemented.  Such
-declarations will be attached to the module, if any, in which they are
-declared.
-
 @item Standard Library Header Units
 The Standard Library is not provided as importable header units.  If
 you want to import such units, you must explicitly build them first.