Fix doctest execution in README (JuliaLang#29778)

The information on how to run doctests in `doc/README.md` wasn't correct. I replaced it with what I found in `CONTRIBUTING.md`.
tekverkp · Oct 23, 2018 · 3d33217 · 3d33217
1 parent 70be5f2
commit 3d33217
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/doc/README.md b/doc/README.md
@@ -23,7 +23,7 @@ from the root directory. This will build the HTML documentation and output it to
 To run the doctests found in the manual run
 
 ```sh
-$ make -C doc check
+$ make -C doc doctest=true
 ```
 
 from the root directory.