UI: Fix context bar being squished

When making the OBS window smaller, the context bar would be cut
in half.

UI/forms/OBSBasic.ui

@@ -215,7 +215,7 @@
       <property name="minimumSize">
        <size>
         <width>0</width>
-        <height>30</height>
+        <height>0</height>
        </size>
       </property>
       <layout class="QHBoxLayout" name="horizontalLayout9">