build: Drop redundant qt/bitcoin.cpp

This file was included in bitcoin#9457, but now it is a part of the
BITCOIN_QT_BASE_CPP.

src/Makefile.qt.include

@@ -364,7 +364,7 @@ $(srcdir)/qt/bitcoinstrings.cpp: FORCE
 
 # The resulted bitcoin_en.xlf source file should follow Transifex requirements.
 # See: https://docs.transifex.com/formats/xliff#how-to-distinguish-between-a-source-file-and-a-translation-file
-translate: $(srcdir)/qt/bitcoinstrings.cpp $(QT_FORMS_UI) $(QT_FORMS_UI) $(BITCOIN_QT_BASE_CPP) qt/bitcoin.cpp $(BITCOIN_QT_WINDOWS_CPP) $(BITCOIN_QT_WALLET_CPP) $(BITCOIN_QT_H) $(BITCOIN_MM)
+translate: $(srcdir)/qt/bitcoinstrings.cpp $(QT_FORMS_UI) $(QT_FORMS_UI) $(BITCOIN_QT_BASE_CPP) $(BITCOIN_QT_WINDOWS_CPP) $(BITCOIN_QT_WALLET_CPP) $(BITCOIN_QT_H) $(BITCOIN_MM)
 	@test -n $(LUPDATE) || echo "lupdate is required for updating translations"
 	$(AM_V_GEN) QT_SELECT=$(QT_SELECT) $(LUPDATE) -no-obsolete -I $(srcdir) -locations relative $^ -ts $(srcdir)/qt/locale/bitcoin_en.ts
 	@test -n $(LCONVERT) || echo "lconvert is required for updating translations"