typo: BFC → NFC

Author: patch

S15-unicode.pod

@@ -704,7 +704,7 @@ Operators between various string types need defining. The general rule should be
         is our Uni type.)
 
 [Note: concatenation and similar operations forming one string from parts can lead to non-NF,
-even between BFC ~ NFC or NFG ~ NFG, if the second string begins with one (or more) "orphan"
+even between NFC ~ NFC or NFG ~ NFG, if the second string begins with one (or more) "orphan"
 combining characters.]
 
 Regexes likely need more work, though I don't see anything immediate.