Fix nonsensical prompt marker

jonasmalacofilho · jonasmalacofilho · commit 23a8f3cb393d · 2019-02-28T14:20:03.000-03:00
diff --git a/README.md b/README.md
@@ -21,7 +21,7 @@ built module can then be loaded with `insmod`; later the module can be removed
 with `rmmod` or `modprobe`.
 
 ```
-> make
+$ make
 # insmod liquidctl.ko
 ```
 
