[FIX] web: correctly set 'text-muted' color value

addons/web/static/src/scss/bootstrap_overridden.scss

@@ -36,6 +36,12 @@ $body-color: $o-main-text-color;
 
 $link-hover-decoration: none;
 
+// Muted
+//
+// Style .text-muted elements
+
+$text-muted: $gray-500 !default;
+
 // Grid columns
 //
 // Set the number of columns and specify the width of the gutters.

addons/web/static/src/scss/webclient.scss

@@ -149,9 +149,6 @@ div.o_boolean_toggle.custom-control.custom-checkbox {
 .text-it {
     font-style: italic;
 }
-.text-muted {
-    color: lighten($text-muted, 10%);
-}
 
 //== Badges
 .badge {