[Glitch] Center 2-columns layout without side effect

Port 7c1ca0c37b to glitch-soc

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/styles/components/columns.scss

@@ -19,7 +19,6 @@
     height: 100%;
 
     &__pane {
-      flex: 1 1 auto;
       height: 100%;
       overflow: hidden;
       pointer-events: none;