sass/_content.scss: decrease min-width of link cards

On my phone they were still overflowing the layout. Also stop fully justifying
the text: with a min-width this small, full justification can look pretty bad,
and left-justification works nicely with the left-hand border lines we now
have.

sass/_content.scss

@@ -90,7 +90,7 @@
 
     .flex-card {
       flex: 1 1;
-      min-width: 15rem;
+      min-width: 10rem;
       margin: 0.8rem;
 
       display: flex;
@@ -104,7 +104,6 @@
       p {
         margin: 0 0 1rem 0;
         flex-grow: 1;
-        text-align: justify;
       }
     }