Remove reference to other problem. Fixes #1.
Remove reference to other problem. Fixes #1.

The problems `simple-linked-list` and `linked-list` should be
independent of each other.

ekse/exercism-common,ErikSchierboom/x-common,Vankog/problem-specifications,Vankog/problem-specifications,jmluy/x-common,kgengler/x-common,jmluy/x-common,rpottsoh/x-common,bennn/x-common,exercism/x-common,jmluy/x-common,exercism/x-common,wobh/x-common,petertseng/x-common,ErikSchierboom/x-common,petertseng/x-common,kgengler/x-common,rpottsoh/x-common