README: remove duplication in maintenance note (#15)

Lil Tricky spotted in e331030#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5

Author: miraclx

README.md

@@ -37,7 +37,7 @@ zlib  - used to compress ID3 frames & expand already compressed frames
 
 ## A note on maintenance!
 
-> I made some fixes to the original project on sourceforge back in in 2009 and
+> I made some fixes to the original project on sourceforge back in 2009 and
 > became the de-facto fork of AtomicParsley as a result.  However, I haven't
 > used this tool myself in many years and have acted in a very loose guiding
 > role since then.