styles: Remove invalid -wekbit-box-align [sic] property.

I’m going to assume that this is not intended to be an optimization
for “WekBit” and can, in fact, be deleted.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

static/styles/portico/portico.scss

@@ -1254,7 +1254,6 @@ input.new-organization-button {
     min-height: 700px;
     display: flex;
     align-items: center;
-    -wekbit-box-align: center;
     justify-content: center;
     text-align: center;
 }