get rid of build_context in example

This is an advanced command and will make life suck for anyone using
it in their project without knowing the consequences.

Author: joufellasfl

README.md

@@ -72,7 +72,6 @@ Here is a sample .cqfdrc file:
     [project]
     org='fooinc'
     name='buildroot'
-    build_context='.'
 
     [build]
     command='make foobar_defconfig && make && asciidoc README.FOOINC'