typo: correct mispelling

Author: alexbosworth

bip-0370.mediawiki

@@ -29,7 +29,7 @@ inputs and outputs be added to the transaction. The fixed global unsigned transa
 cannot be changed which prevents any additional inputs or outputs to be added.
 PSBT Version 2 is intended to rectify this problem.
 
-An additional benficial side effect is that all information for a given input or output will be
+An additional beneficial side effect is that all information for a given input or output will be
 provided by its <tt><input-map></tt> or <tt><output-map></tt>. With Version 0, to retrieve
 all of the information for an input or output, data would need to be found in two locations:
 the <tt><input-map></tt>/<tt><output-map></tt> and the global unsigned transaction. PSBT