fix: unresponsive modal in student dashboard view (#31432)

issue: https://github.com/openedx/build-test-release-wg/issues/228

Co-authored-by: Edward Zarecor <ezarecor@tcril.org>

lms/static/sass/multicourse/_dashboard.scss

@@ -1643,6 +1643,12 @@ a.fade-cover {
 #unenroll-modal {
   margin-top: -60px;
 
+  @media (max-width: 640px) {
+    width: 82% !important;
+    margin-left: -41% !important;
+    box-sizing: border-box;
+  }
+
   .modal-form-error {
     background: tint($red, 95%);
     margin-left: $baseline;
@@ -1650,6 +1656,16 @@ a.fade-cover {
   }
 }
 
+#email-settings-modal {
+  margin-top: -60px;
+
+  @media (max-width: 640px) {
+    width: 82% !important;
+    margin-left: -41% !important;
+    box-sizing: border-box;
+  }
+}
+
 #activate-account-modal {
     display: block;
     position: fixed;