theme: Normalize entry focus style

This fixes the focus style of the regular entry to match with the GTK
one.

This will allow removing a number of overrides of entries for
normalization.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/931

data/theme/gnome-shell-sass/_drawing.scss

@@ -46,6 +46,7 @@
     border-color: if($fc==$selected_bg_color,
               $selected_borders_color,
               darken($fc,35%));
+    box-shadow: inset 0 0 0 1px $fc;
   }
   @if $t==hover { }
   @if $t==insensitive {

data/theme/gnome-shell-sass/widgets/_entries.scss

@@ -7,7 +7,7 @@ StEntry {
   color: $fg_color;
   @include entry(normal);
   //&:hover { @include entry(hover);}
-  &:focus { @include entry(focus,$fc:transparentize($fg_color,0.5));}
+  &:focus { @include entry(focus);}
   &:insensitive { @include entry(insensitive);}
   selection-background-color: $selected_bg_color;
   selected-color: $selected_fg_color;