Rename "Stop" Emulator to "Exit" in README.md

The term “Exit” more accurately reflects that this key sequence
terminates the emulator’s execution loop rather than simply pausing
or stopping it.

Author: otischung

README.md

@@ -44,7 +44,7 @@ containing concatenated `bootsect.o + setup.o + misc.o + piggy.o`. `initrd` is t
 initial RAM disk image, which is an optional argument.
 `disk-image` is the path to disk image which can be mounted as a block device via virtio. For the reference Linux guest, ext4 filesystem is used for disk image.
 
-### Stop Emulator
+### Exit Emulator
 
 To exit kvm-host, press "Ctrl-A", release both keys, and then press "x".