scripted-diff: Use new FUZZ_TARGET macro everywhere

-BEGIN VERIFY SCRIPT-

  ren() { sed --regexp-extended -i "s|$1|$2|g" $(git grep -l --extended-regexp "$1"); }

  # Replace FUZZ_TARGET_INIT
  ren 'FUZZ_TARGET_INIT\((.+), (.+)\)' 'FUZZ_TARGET(\1, .init = \2)'

  # Delete unused FUZZ_TARGET_INIT
  sed -i -e '37,39d' src/test/fuzz/fuzz.h

-END VERIFY SCRIPT-

src/test/fuzz/script_sign.cpp

@@ -30,7 +30,7 @@ void initialize_script_sign()
     SelectParams(ChainType::REGTEST);
 }
 
-FUZZ_TARGET_INIT(script_sign, initialize_script_sign)
+FUZZ_TARGET(script_sign, .init = initialize_script_sign)
 {
     FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
     const std::vector<uint8_t> key = ConsumeRandomLengthByteVector(fuzzed_data_provider, 128);