Revert "Failing test case requiring rb_str_modify"
Revert "Failing test case requiring rb_str_modify"

This reverts commit 05227e9494221a28518858dab034400fc4d327ce.

sparkchaser/ffi,MikaelSmith/ffi,mvz/ffi,yghannam/ffi,mvz/ffi,sparkchaser/ffi,MikaelSmith/ffi,majioa/ffi,tduehr/ffi,ferventcoder/ffi,yghannam/ffi,majioa/ffi,mvz/ffi,yghannam/ffi,sparkchaser/ffi,MikaelSmith/ffi,ferventcoder/ffi,tduehr/ffi,sparkchaser/ffi,MikaelSmith/ffi,mvz/ffi,ferventcoder/ffi,ffi/ffi,ferventcoder/ffi,majioa/ffi,tduehr/ffi,yghannam/ffi,ffi/ffi,tduehr/ffi,majioa/ffi,yghannam/ffi,ffi/ffi