Remove duplicate CSS properties (#16278)

app/javascript/styles/mailer.scss

@@ -258,7 +258,6 @@ h5 {
     padding: 16px;
     line-height: 20px;
     mso-line-height-rule: exactly;
-    border-radius: 4px;
     text-align: center;
     font-weight: 500;
     font-size: 17px;

app/javascript/styles/mastodon/about.scss

@@ -322,7 +322,6 @@ $small-breakpoint: 960px;
     font-family: $font-sans-serif, sans-serif;
     font-size: 16px;
     font-weight: 400;
-    font-size: 16px;
     line-height: 30px;
     margin-bottom: 12px;
     color: $darker-text-color;

app/javascript/styles/mastodon/widgets.scss

@@ -593,7 +593,6 @@ $fluid-breakpoint: $maximum-width + 20px;
     display: block;
     font-weight: 500;
     padding: 15px;
-    overflow: hidden;
     white-space: nowrap;
     overflow: hidden;
     text-overflow: ellipsis;