QGLShaderProgram: replace a Q_FOREACH with qDeleteAll()

Change-Id: I81a7a3accdcbd3229aeb1dc6fcda5b4ae5cd1a7b
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

src/opengl/qglshaderprogram.cpp

@@ -882,10 +882,8 @@ void QGLShaderProgram::removeAllShaders()
             }
         }
     }
-    foreach (QGLShader *shader, d->anonShaders) {
-        // Delete shader objects that were created anonymously.
-        delete shader;
-    }
+    // Delete shader objects that were created anonymously.
+    qDeleteAll(d->anonShaders);
     d->shaders.clear();
     d->anonShaders.clear();
     d->linked = false;  // Program needs to be relinked.