Fix comment (opcode -> instruction)

src/string.asm

@@ -121,7 +121,7 @@ strclr:
 ;----- strlclr(char* str, int size) -----;
 ; Replaces characters of a string with \0, using arg size
 ; <!> DANGEROUS FUNCTION, it might exceed string boundaries if used incorrectly. Use strclr() instead!
-; Function has no return value, rax will be 0 (0x0 stored in rax for opcode stosb)
+; Function has no return value, rax will be 0 (0x0 stored in rax for instruction stosb)
 strlclr:
 	mov	rcx, rsi
 	xor	rax, rax