refactor: finished converting sass colors in _session_password.scss

stylesheets/_session.scss

@@ -824,7 +824,7 @@ label {
       background: var(--color-cell-background);
       color: var(--color-text);
 
-      border: 1px solid $session-shade-8;
+      border: 1px solid var(--color-darker-gray-color);
       border-radius: 5px;
     }
   }

stylesheets/_session_constants.scss

@@ -102,7 +102,6 @@ $session-shade-5: #222325;
 $session-shade-6: #232323;
 $session-shade-6-alt: #2c2c2c;
 $session-shade-7: #2e2e2e;
-$session-shade-8: #2f2f2f;
 $session-shade-9: #313131;
 $session-shade-10: #3e3e3e;
 $session-shade-11: #3f3f3f;

stylesheets/_session_password.scss

@@ -57,7 +57,7 @@
       padding: 3 * $session-margin-lg 2 * $session-margin-lg;
       box-sizing: border-box;
       background-color: var(--color-darkest-gray-color);
-      border: 1px solid $session-shade-8;
+      border: 1px solid var(--color-darker-gray-color);
       border-radius: 2px;
 
       .warning-info-area,