fix: keep the key name without line breaks

Author: leezng

src/components/TreeNode/styles.less

@@ -83,6 +83,10 @@
   color: @comment-color;
 }
 
+.@{css-prefix}-key {
+  white-space: nowrap;
+}
+
 .@{css-prefix}-value {
   word-break: break-word;
 }