Fix comment for number of sectors to read

Author: maxkl

07-bootsector-disk/boot_sect_main.asm

@@ -3,7 +3,7 @@
     mov sp, bp
 
     mov bx, 0x9000 ; es:bx = 0x0000:0x9000 = 0x09000
-    mov dh, 2 ; read 5 sectors
+    mov dh, 2 ; read 2 sectors
     ; the bios sets 'dl' for our boot disk number
     ; if you have trouble, use the '-fda' flag: 'qemu -fda file.bin'
     call disk_load