[Bug libstdc++/59530] Incorrect check on string_view operator[]

[3dw4rd at verizon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59530

--- Comment #1 from Ed Smith-Rowland <3dw4rd at verizon dot net> ---
I mistakenly took cases for string which must be null terminated.
I think we'll just remove those lines from the testcases.