Update libplacebo, sdl2-compat, and SDL3

.github/workflows/build-appimage.yml

@@ -42,7 +42,7 @@ jobs:
         uses: actions/checkout@v5
         with:
           repository: libsdl-org/SDL
-          ref: ddba673cddfa79ce798eca5ba402e0f1a2a2a243
+          ref: release-3.4.18
           path: deps/SDL
 
       - name: Build SDL3
@@ -56,7 +56,7 @@ jobs:
         uses: actions/checkout@v5
         with:
           repository: libsdl-org/sdl2-compat
-          ref: release-2.32.70
+          ref: release-2.32.74
           path: deps/sdl2-compat
 
       - name: Build sdl2-compat
@@ -101,7 +101,7 @@ jobs:
         uses: actions/checkout@v5
         with:
           repository: haasn/libplacebo
-          ref: e2972fdd09adacd383656738d7d280f0cd84a761
+          ref: 92b5ac6db79f4d680eb656692f7bf51e9606f42a
           path: deps/libplacebo
           submodules: 'recursive'