Effect: Call glFinish before providing VFP output texture

glFinish should be called before reading from a texture, to make sure it's been
properly rendered to.

PiperOrigin-RevId: 527302946

library/effect/src/main/java/com/google/android/exoplayer2/effect/FinalShaderProgramWrapper.java

@@ -341,6 +341,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
         outputTexture.fboId, outputTexture.width, outputTexture.height);
     GlUtil.clearOutputFrame();
     checkNotNull(defaultShaderProgram).drawFrame(inputTexture.texId, presentationTimeUs);
+    GLES20.glFinish();
     checkNotNull(textureOutputListener).onTextureRendered(outputTexture, presentationTimeUs);
   }