docs/relnotes: document the removal of GALLIUM_MSAA

Cc: 10.2.10.3 10.4 <mesa-stable@lists.freedesktop.org>
(cherry picked from commit ac319d94d3)

docs/relnotes/10.2.html

@@ -88,6 +88,8 @@ following options during configure, if you would like support for svga driver
 Note: The files are installed in $(libdir)/gallium-pipe/ and the interface
 between them and libxatracker.so is <strong>not</strong> stable.
 </p>
+
+<li>The environment variable GALLIUM_MSAA that forced a multisample GLX visual was removed.</li>
 </ul>
 
 </div>

docs/relnotes/10.3.html

@@ -327,6 +327,7 @@ DRM drivers that don't have a full-fledged GEM (such as qxl or simpledrm)</li>
 <li>Removed support for the GL_ATI_envmap_bumpmap extension</li>
 <li>The hacky --enable-32/64-bit is no longer available in configure. To build
 32/64 bit mesa refer to the default method recommended by your distribution</li>
+</li>The environment variable GALLIUM_MSAA that forced a multisample GLX visual was removed.</li>
 </ul>
 
 </div>

docs/relnotes/10.4.html

@@ -59,6 +59,7 @@ TBD.
 <h2>Changes</h2>
 
 <ul>
+<li>The environment variable GALLIUM_MSAA that forced a multisample GLX visual was removed.</li>
 </ul>
 
 </div>