scripted-diff: Replace UINT256_ONE() with uint256::ONE

-BEGIN VERIFY SCRIPT-
sed -i '/inline.* UINT256_ONE() {/,+1d' src/uint256.h
sed -i 's/UINT256_ONE()/uint256::ONE/' $(git grep -l UINT256_ONE)
-END VERIFY SCRIPT-

src/uint256.h

@@ -150,6 +150,4 @@ inline uint256 uint256S(const std::string& str)
     return rv;
 }
 
-inline const uint256& UINT256_ONE() { return uint256::ONE; }
-
 #endif // BITCOIN_UINT256_H