Remove "Id" entries from test_plugincontroller JSON files

This eliminates 5 very similar QINFO lines from the output of
test_plugincontroller:
QINFO  : TestPluginController::initTestCase() kf.coreaddons: The plugin
"/path/to/kdevelop/build/kdevplatform/shell/tests/testplugindir/kdevplatform/60/test_projectdefault.so"
explicitly states an 'Id' in the embedded metadata. This value should be
removed, the resulting pluginId will not be affected by it