Remove Travis config for non-existent '--with-winmm' option

.travis.yml

@@ -26,12 +26,6 @@ matrix:
   - os: linux
     env: HOST="" API="oss"
     compiler: clang
-  - os: linux
-    env: HOST="--host=i686-w64-mingw32" API="winmm" CPPFLAGS="-Wno-unused-function"
-    compiler: gcc
-  - os: linux
-    env: HOST="--host=x86_64-w64-mingw32" API="winmm" CPPFLAGS="-Wno-unused-function"
-    compiler: gcc
   - os: linux
     env: HOST="--host=i686-w64-mingw32" API="dsound" CPPFLAGS="-Wno-unused-function"
     compiler: gcc