Fixed typo in README.md

Author: mimshipio

README.md

@@ -249,7 +249,7 @@ Footnotes
 
 <a name="flashdetect">[2]</a> Flash memory size detection does not work in some cases. These can be configured at runtime, but filing a bug is recommended if such a case is encountered.
 
-<a name="osxver">[3]</a> 10.9 is only needed for the Qt port. It may be possible to build or running the Qt port on 10.7 or older, but this is not officially supported. The SDL port is known to work on 10.5, and may work on older.
+<a name="osxver">[3]</a> 10.9 is only needed for the Qt port. It may be possible to build or run the Qt port on 10.7 or older, but this is not officially supported. The SDL port is known to work on 10.5, and may work on older.
 
 [downloads]: http://mgba.io/downloads.html
 [source]: https://github.com/mgba-emu/mgba/