Fix typo in input placeholder color class

Author: Alejandro Celaya

src/components/input/Input.tsx

@@ -16,7 +16,7 @@ export function inputStyles({ classes, feedback }: InputStylesOptions) {
   return classnames(
     'focus-visible-ring ring-inset border rounded w-full p-2',
     'bg-grey-0 focus:bg-white disabled:bg-grey-1',
-    'placeholder:text-color-grey-5 disabled:placeholder:color-grey-6',
+    'placeholder:text-grey-6 disabled:placeholder:text-grey-7',
 
     // On iOS, the input font size must be at least 16px to prevent the browser
     // from zooming into it on touch.