Use nested class instead of space separated classes

apps/client/src/styles.scss

@@ -103,7 +103,8 @@ body {
         color: rgba(var(--light-primary-text));
       }
 
-      &.mat-select-disabled .mat-select-placeholder {
+      &.mat-select-disabled {
+        .mat-select-placeholder {
           color: rgba(
             var(--palette-foreground-disabled-text-dark),
             var(--palette-foreground-disabled-text-dark-alpha)
@@ -111,6 +112,7 @@ body {
         }
       }
     }
+  }
 }
 
 button:focus {
@@ -247,10 +249,12 @@ ngx-skeleton-loader {
     color: rgba(var(--dark-primary-text));
   }
 
-  &.mat-select-disabled .mat-select-placeholder {
+  &.mat-select-disabled {
+    .mat-select-placeholder {
       color: rgba(
         var(--palette-foreground-disabled-text),
         var(--palette-foreground-disabled-text-alpha)
       );
     }
+  }
 }