Revert "ci: mingw - build dependency libopus"

This reverts commit 0ca98f8.

.github/workflows/mingw.yml

@@ -51,12 +51,6 @@ jobs:
         path: baresip-win32/openssl
         key: ${{ runner.os }}-mingw-openssl-3.0.7
 
-    - uses: actions/cache@v4
-      id: libopus
-      with:
-        path: baresip-win32/opus
-        key: ${{ runner.os }}-mingw-opus-1.5.2
-
     - name: "build openssl"
       if: steps.openssl.outputs.cache-hit != 'true'
       run: |
@@ -65,14 +59,6 @@ jobs:
         mv openssl-3.0.7 baresip-win32/openssl
         make -j$(nproc) -C baresip-win32 openssl
 
-    - name: "build opus"
-      if: steps.opus.outputs.cache-hit != 'true'
-      run: |
-        wget https://downloads.xiph.org/releases/opus/opus-1.5.2.tar.gz
-        tar -xzf opus-1.5.2.tar.gz
-        mv opus-1.5.2 baresip-win32/opus
-        make -j$(nproc) -C baresip-win32 opus
-
     - name: "build"
       run: make -j$(nproc) -C baresip-win32 baresip