Fix button styles on CS2 and project screen

Id5d62b830 was trying to fix wrong ActionButton style on project info
screen, but broke the style on CS2 instead. Fix it in both places.

Test Plan:

Deploy cookbook-plugin and verify the style of "Say hello" button.
Verify the style of "Create change" button on project info screen.

Bug: issue 2906
Change-Id: Ia2a46e83ebe780c6b3304a8aba97aa7876dba2fa

gerrit-gwtui/src/main/java/com/google/gerrit/client/actions/ActionButton.java

@@ -68,6 +68,7 @@ public class ActionButton extends Button implements ClickHandler {
       .openDiv()
       .append(action.label())
       .closeDiv());
+    setStyleName("");
     setTitle(action.title());
     setEnabled(action.enabled());
     addClickHandler(this);

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/ProjectInfoScreen.java

@@ -584,6 +584,7 @@ public class ProjectInfoScreen extends ProjectScreen {
 
   private Button createChangeAction() {
     final Button createChange = new Button(Util.C.buttonCreateChange());
+    createChange.setStyleName("");
     createChange.setTitle(Util.C.buttonCreateChangeDescription());
     createChange.addClickHandler(new ClickHandler() {
       @Override