Remove superscript tag and just use superscript characters in README.md

README.md

@@ -122,7 +122,7 @@ period of execution.  On some systems, this was happening within 10 - 15
 minutes.  Due to the extent of scope, rollover handling has not been
 implemented at this time; however, the cycle counter was increased in size
 from a 32-bit signed integer to a 64-bit signed integer (long long), extending
-the duration before rollover by 4,294,967,295 (2[sup]32[/sup]) times.
+the duration before rollover by 4,294,967,295 (2³²) times.
 Hopefully that is more than adequate for normal use.  :-)  This change
 touches a number of different areas—each one of which needed to be
 adjusted for the increased integer size—, so it is possible that if an area