Reset input capacity when setting external shader program

Before this CL, externalShaderProgramInputCapacity was not reset when
the external shader program was reset (which occurs when  the
InputSwitcher switches to an input with a different ColorInfo). This is
due to a regression introduced in bef3d51.

PiperOrigin-RevId: 637869215

libraries/effect/src/main/java/androidx/media3/effect/ExternalTextureManager.java

@@ -191,6 +191,7 @@ public void releaseAllRegisteredFrames() {
   @Override
   public void setSamplingGlShaderProgram(GlShaderProgram samplingGlShaderProgram) {
     checkState(samplingGlShaderProgram instanceof ExternalShaderProgram);
+    externalShaderProgramInputCapacity.set(0);
     this.externalShaderProgram = (ExternalShaderProgram) samplingGlShaderProgram;
   }