fix(filmstrip-only): set width for toolbar popovers

The popovers in filmstrip only are displaying thinly.
As a quick workaround, set a width on them. There
should only be one anyway, which shows up when
talking while muted.

css/_toolbars.scss

             width: 37px;
         }
 
+        .button-popover-message {
+            width: 100px;
+        }
+
         .toolbar-button-wrapper:first-child .button {
             border-top-left-radius: 3px;
             border-top-right-radius: 3px;

react/features/toolbox/components/ToolbarButton.web.js

 
             children = ( // eslint-disable-line no-extra-parens
                 <InlineDialog
-                    content = { t(dataAttr, dataInterpolate) }
+                    content = {
+                        <div className = 'button-popover-message'>
+                            { t(dataAttr, dataInterpolate) }
+                        </div>
+                    }
                     isOpen = { Boolean(popupConfig) }
                     position = { position }>
                     { buttonComponent }