doc: Fix title "String Constants"
doc: Fix title "String Constants"

Cut & paste oops...

turingstudio/nasm,techkey/nasm,letolabs/nasm,projedi/nasm,projedi/nasm,techkey/nasm,techkey/nasm,techkey/nasm,letolabs/nasm,Distrotech/nasm,projedi/nasm,Distrotech/nasm,letolabs/nasm,Distrotech/nasm,turingstudio/nasm,projedi/nasm,Distrotech/nasm,techkey/nasm,turingstudio/nasm,turingstudio/nasm,projedi/nasm