Remove conflicting theme overrides

Fix #21

styles/theme-overrides.less

@@ -1,40 +1,31 @@
-// One Dark
+atom-workspace {
+  // Atom Material
+  &.theme-atom-material-ui {
+    // Tab Bar
+    .tab-bar .tab {
+      .title:before {
+        margin-left: 0;
+        margin-right: 5px !important;
+        position: relative;
+        vertical-align: middle;
+      }
 
-[theme-one-dark-ui-layoutmode],
-[theme-one-light-ui-layoutmode] {
-  .list-group,
-  .list-tree {
-    .icon::before {
-      vertical-align: bottom;
-    }
-  }
-}
-
-atom-workspace.theme-atom-material-ui {
-  // Tab Bar
-  .tab-bar .tab {
-    .title:before {
-      margin-left: 0;
-      margin-right: 5px !important;
-      position: relative;
-      vertical-align: middle;
+      .title.icon:before {
+        vertical-align: text-bottom;
+      }
     }
 
-    .title.icon:before {
-      vertical-align: text-bottom;
+    .icon-file-directory {
+      &:before {
+        margin-right: 10px !important;
+      }
     }
-  }
-
-  .icon-file-directory {
-    &:before {
-      margin-right: 10px !important;
-    }
-  }
 
-  .icon-file-text,
-  .icon-book {
-    &:before {
-      top: 6px;
+    .icon-file-text,
+    .icon-book {
+      &:before {
+        top: 6px;
+      }
     }
   }
 }