user-profile: Change color of `name` field.

With the previous color it was hard to read the text and
also that color does not matches with the zulip style.

This commit changes the color of `name` field for
user-profile modal for better visability both in day
and night mode.

static/styles/night_mode.scss

@@ -620,6 +620,24 @@ on a dark background, and don't change the dark labels dark either. */
         box-shadow: 0 5px 10px hsla(0, 0%, 0%, 0.4);
     }
 
+    #user-profile-modal {
+        #default-section {
+            .default-field {
+                .name {
+                    color: hsl(236, 33%, 90%);
+                }
+            }
+        }
+
+        #content {
+            .field-section {
+                .name {
+                    color: hsl(236, 33%, 90%);
+                }
+            }
+        }
+    }
+
     /* Arrows: */
     .hotspot.overlay {
         .hotspot-popover.arrow-right::before {

static/styles/popovers.scss

@@ -286,9 +286,10 @@ ul {
             margin-bottom: 5px;
 
             .name {
-                color: hsl(0, 0%, 55%);
+                color: hsl(0, 0%, 20%);
                 display: inline-block;
                 min-width: 120px;
+                font-weight: 600;
             }
         }
 
@@ -322,7 +323,8 @@ ul {
             margin-top: 8px;
 
             .name {
-                color: hsl(0, 0%, 55%);
+                color: hsl(0, 0%, 20%);
+                font-weight: 600;
             }
 
             .value {