ci: Drop ENABLE_HARDENING=OFF from clang-tidy

It's not clear why this was added in the first place, but it is not
necessary currently.

bitcoin/bitcoin#32038 (comment)
bitcoin/bitcoin#24753.

Author: davidgumberg

ci/test/00_setup_env_native_tidy.sh

@@ -20,7 +20,6 @@ export RUN_TIDY=true
 export GOAL="install"
 export BITCOIN_CONFIG="\
  -DWITH_ZMQ=ON -DBUILD_GUI=ON -DBUILD_BENCH=ON -DWITH_USDT=ON -DWITH_BDB=ON -DWARN_INCOMPATIBLE_BDB=OFF \
- -DENABLE_HARDENING=OFF \
  -DCMAKE_C_COMPILER=clang-${TIDY_LLVM_V} \
  -DCMAKE_CXX_COMPILER=clang++-${TIDY_LLVM_V} \
  -DCMAKE_C_FLAGS_RELWITHDEBINFO='-O0 -g0' \