Merge pull request #22496 from overleaf/mf-login-register-use-social-button

[web] Use `.btn-social` for all login and register buttons that has icon on it

GitOrigin-RevId: a5590578ebf048b188d9f9ab3551907fdf5fe63d

services/web/frontend/stylesheets/bootstrap-5/pages/login-register.scss

@@ -1,21 +1,3 @@
-.login-btn {
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  padding: var(--spacing-02) 0;
-}
-
-.login-btn-icon {
-  position: relative;
-  top: unset;
-  left: unset;
-  background: unset;
-  border-radius: unset;
-  width: 20px;
-  height: 20px;
-  margin-right: var(--spacing-02);
-}
-
 .login-register-or-text-container {
   padding: var(--spacing-08) 0 var(--spacing-05) 0;
   margin: 0;