Remove no longer used old settings styles

[MAILPOET-2770]

assets/css/src/components-plugin/_settings.scss

@@ -1,54 +0,0 @@
-#mailpoet_settings {
-  .mailpoet_tab_panel {
-    display: none;
-  }
-
-  .form-table th {
-    width: 20em;
-  }
-
-  .tooltip.dashicons.dashicons-editor-help {
-    line-height: 1.4;
-  }
-
-  .sending-free-plan-button {
-    background: #ff5301;
-    border-color: #e64c03;
-    box-shadow: 0 1px 0 #e64c03;
-    margin: 10px 0;
-    text-shadow: 0 -1px 1px #e64c03;
-
-    strong {
-      text-transform: uppercase;
-    }
-  }
-
-  .mailpoet_success_item:before {
-    content: '✔ ';
-  }
-
-  .mailpoet_error_item:before {
-    content: '✗ ';
-  }
-
-  .mailpoet_woocommerce_editor_button {
-    margin-top: 10px;
-  }
-
-  @include breakpoint-max-width(782px) {
-    .form-table th {
-      width: auto;
-    }
-
-    .mailpoet_sending_methods {
-      flex-flow: row wrap;
-      justify-content: space-around;
-
-      > li {
-        flex-basis: auto;
-        margin-right: 0;
-      }
-    }
-  }
-
-}