revert: new util class expected for return errors by more convenient way

reverts:
- bb1d46c

Author: kwvg

contrib/devtools/copyright_header.py

@@ -25,7 +25,6 @@
     'src/ctpl_stl.h',
     'src/test/fuzz/FuzzedDataProvider.h',
     'src/tinyformat.h',
-    'src/util/expected.h',
     'src/wallet/bip39.cpp',
     'src/wallet/bip39.h',
     'src/wallet/bip39_english.h',

src/Makefile.am

@@ -357,7 +357,6 @@ BITCOIN_CORE_H = \
   util/enumerate.h \
   util/epochguard.h \
   util/error.h \
-  util/expected.h \
   util/fastrange.h \
   util/fees.h \
   util/golombrice.h \