fix members ui for light mode

stylesheets/_modules.scss

@@ -1203,7 +1203,9 @@
 }
 
 .module-message-detail__unix-timestamp {
-  color: $color-light-10;
+  @include themify($themes) {
+    color: subtle(themed('textColor'));
+  }
 }
 
 .module-message-detail__delete-button-container {

stylesheets/_session.scss

@@ -370,7 +370,10 @@ $session-element-border-green: 4px solid $session-color-green;
   font-size: $session-font-md;
 
   &-text {
-    @include session-color-subtle($session-color-white);
+    @include themify($themes) {
+      @include session-color-subtle(themed('textColor'));
+    }
+
     font-family: $session-font-default;
     font-weight: 300;
     font-size: $session-font-xs;

stylesheets/_theme_dark.scss

@@ -604,10 +604,6 @@
 
   // Module: Message Detail
 
-  .module-message-detail__unix-timestamp {
-    color: $color-dark-55;
-  }
-
   .module-message-detail__delete-button {
     background-color: $session-color-danger;
     color: $color-white;