relocate css about custom-control-label

src/client/styles/scss/_admin.scss

@@ -156,10 +156,6 @@
       background-color: rgba($info, 0.1);
     }
   }
-
-  label.custom-control-label {
-    font-weight: normal;
-  }
 }
 
 .admin-navigation > a + a {

src/client/styles/scss/atoms/_custom_control.scss

@@ -0,0 +1,3 @@
+label.custom-control-label {
+  font-weight: normal;
+}

src/client/styles/scss/style-app.scss

@@ -18,6 +18,7 @@
 @import 'atoms/buttons';
 @import 'atoms/nav';
 @import 'atoms/spinners';
+@import 'atoms/custom_control';
 
 // crowi component
 @import 'admin';