Update configuring_arrayfire_environment.md
Update configuring_arrayfire_environment.md

Fixed wrong description of default behavior when AF_MEM_DEBUG is not set.
arrayfire/arrayfire,umar456/arrayfire,arrayfire/arrayfire,9prady9/arrayfire,umar456/arrayfire,arrayfire/arrayfire,umar456/arrayfire,9prady9/arrayfire,umar456/arrayfire,9prady9/arrayfire,9prady9/arrayfire,arrayfire/arrayfire