Make placeholder more grey when no input (fixes #17243)

The placeholder is actually the label in this case.

res/css/views/auth/_AuthBody.scss

@@ -58,10 +58,6 @@ limitations under the License.
         background-color: $authpage-body-bg-color;
     }
 
-    .mx_Field label {
-        color: $authpage-primary-color;
-    }
-
     .mx_Field_labelAlwaysTopLeft label,
     .mx_Field select + label /* Always show a select's label on top to not collide with the value */,
     .mx_Field input:focus + label,

res/css/views/elements/_Field.scss

@@ -100,7 +100,6 @@ limitations under the License.
         color 0.25s ease-out 0.1s,
         transform 0.25s ease-out 0.1s,
         background-color 0.25s ease-out 0.1s;
-    color: $primary-content;
     background-color: transparent;
     font-size: $font-14px;
     transform: translateY(0);