doc: fix doconly to docopen

AyushG3112 · AyushG3112 · commit b971a1efd29e · 2018-03-26T10:19:14.000+05:30
PR-URL: #19321
diff --git a/BUILDING.md b/BUILDING.md
@@ -210,7 +210,7 @@ If you prefer to read the documentation in the browser,
 run the following once `make doc` is done:
 
 ```console
-$ make doconly
+$ make docopen
 ```
 
 This will open up a browser tab/window with the documentation.
