Improve readability of slow external clock (#425)

* improve readability of slow external clock

* article update (an to a) regular

* use colon to denote example

Co-authored-by: Eldred Habert <[email protected]>

Author: splch

src/Serial_Data_Transfer_(Link_Cable).md

@@ -71,11 +71,10 @@ The external clock is typically supplied by another Game Boy, but might
 be supplied by another computer (for example if connected to a PC's
 parallel port), in that case the external clock may have any speed. Even
 the old/monochrome Game Boy is reported to recognize external clocks of
-up to 500 kHz. And there is no limitation into the other direction - even
-when suppling an external clock speed of "1 bit per month", then the
-Game Boy will still eagerly wait for the next bit(s) to be transferred.
-It isn't required that the clock pulses are sent at an regular interval
-either.
+up to 500 kHz. And there is no limitation in the other direction: even
+when suppling an external clock speed of "1 bit per month," the Game Boy
+will eagerly wait for the next bit to be transferred. It isn't required
+that the clock pulses are sent at a regular interval either.
 
 ## Timeouts