fix typo

Author: coke

doc/Type/Str.pod6

@@ -520,7 +520,7 @@ For integer conversions, specifying a precision implies that the
 output of the number itself should be zero-padded to this width, where
 the C<0> flag is ignored:
 
-(Note that this feature currenly works for unsigned integer conversions, but not
+(Note that this feature currently works for unsigned integer conversions, but not
 for signed integer.)
 
   NYI sprintf '<%.6d>', 1;      # "<000001>"