UI: Add frame around transitions dock

The transitions dock doesn't have a proper container, like
the other docks.

UI/forms/OBSBasic.ui

@@ -1134,35 +1134,44 @@
    </attribute>
    <widget class="QWidget" name="dockWidgetContents_5">
     <layout class="QVBoxLayout" name="verticalLayout_3">
+     <property name="spacing">
+      <number>0</number>
+     </property>
      <property name="leftMargin">
-      <number>4</number>
+      <number>0</number>
      </property>
      <property name="topMargin">
-      <number>4</number>
+      <number>0</number>
      </property>
      <property name="rightMargin">
-      <number>4</number>
+      <number>0</number>
      </property>
      <property name="bottomMargin">
-      <number>4</number>
+      <number>0</number>
      </property>
      <item>
-      <widget class="QFrame" name="transitionsContainer">
-       <layout class="QVBoxLayout" name="verticalLayout_2">
+      <widget class="QFrame" name="transitionsFrame">
+       <property name="frameShape">
+        <enum>QFrame::StyledPanel</enum>
+       </property>
+       <property name="frameShadow">
+        <enum>QFrame::Sunken</enum>
+       </property>
+       <layout class="QVBoxLayout" name="verticalLayout_8">
         <property name="spacing">
          <number>2</number>
         </property>
         <property name="leftMargin">
-         <number>0</number>
+         <number>4</number>
         </property>
         <property name="topMargin">
-         <number>0</number>
+         <number>4</number>
         </property>
         <property name="rightMargin">
-         <number>0</number>
+         <number>4</number>
         </property>
         <property name="bottomMargin">
-         <number>0</number>
+         <number>4</number>
         </property>
         <item>
          <widget class="QComboBox" name="transitions">