styles: Inline obsolete border-radius mixin

This CSS property is supported by all of our target browsers by now

see https://caniuse.com/#feat=border-radius

Author: Turbo87

app/styles/_helpers.scss

@@ -1,10 +1,3 @@
-@mixin border-radius($radius) {
-    -webkit-border-radius: $radius;
-       -moz-border-radius: $radius;
-        -ms-border-radius: $radius;
-            border-radius: $radius;
-}
-
 @mixin vertical-gradient($start, $end) {
     background: $end;
     background: -moz-linear-gradient(top, $start 0%, $end 100%);

app/styles/app.scss

@@ -48,7 +48,7 @@ body > div {
   margin-bottom: 10px;
   background-color: $main-bg;
   padding: 15px;
-  @include border-radius(10px);
+  border-radius: 10px;
   box-shadow: 0px 0px 5px 2px #3b6837;
   border: 5px solid #62865f;
   color: $main-color;
@@ -131,7 +131,7 @@ body > div {
     background-repeat: no-repeat;
     background-position: 6px 6px;
     background-size: 14px 15px;
-    @include border-radius(15px);
+    border-radius: 15px;
 }
 
 form.search label {
@@ -206,7 +206,7 @@ span.loading {
     text-align: center;
     margin: 0 0 10px 0;
     padding: 10px;
-    @include border-radius(5px);
+    border-radius: 5px;
 
     &.shown {
         display: block;
@@ -287,7 +287,7 @@ ul.dropdown {
     list-style: none;
     z-index: 10;
     overflow: hidden;
-    @include border-radius(5px);
+    border-radius: 5px;
 
     li a {
         font-size: 90%;

app/styles/crate.scss

@@ -3,7 +3,7 @@
     padding: 20px;
     background-color: $main-bg-dark;
     margin-bottom: 20px;
-    @include border-radius(5px);
+    border-radius: 5px;
     display: flex;
     flex-wrap: wrap;
     align-items: center;
@@ -61,7 +61,7 @@
     display: flex;
     justify-content: space-between;
     padding: 20px;
-    @include border-radius(5px);
+    border-radius: 5px;
     background-color: white;
     margin-bottom: 40px;
 
@@ -123,7 +123,7 @@
         background-color: $main-bg-dark;
         padding: 10px;
         display: inline-block;
-        @include border-radius(5px);
+        border-radius: 5px;
     }
 }
 

app/styles/home.scss

@@ -11,7 +11,7 @@
     font-weight: bold;
     border: none;
     outline: 0;
-    @include border-radius(30px);
+    border-radius: 30px;
     @include vertical-gradient($start, $end);
 
     img, svg {
@@ -35,7 +35,7 @@
 
 button.small {
     padding: 10px 20px;
-    @include border-radius(30px);
+    border-radius: 30px;
 }
 
 .tan-button {