Merge bitcoin/bitcoin#31804: ci: Remove no longer needed `-Wno-error=…

…documentation`

f1d7a6d ci: Remove no longer needed '-Wno-error=documentation' (Hennadii Stepanov)

Pull request description:

  Picked from bitcoin/bitcoin#31726.

ACKs for top commit:
  maflcko:
    lgtm ACK f1d7a6d

Tree-SHA512: 2c4b197da1a60662922341062f9c1fe43b0e35a50194f4757057a48d7538f2f68540ed56508193a5c6a81e3f7dfbca78b15e3c101aae08d8ccd1fc5df0535932

ci/test/00_setup_env_i686_multiprocess.sh

@@ -18,7 +18,6 @@ export BITCOIN_CONFIG="\
  -DCMAKE_BUILD_TYPE=Debug \
  -DCMAKE_C_COMPILER='clang;-m32' \
  -DCMAKE_CXX_COMPILER='clang++;-m32' \
- -DCMAKE_CXX_FLAGS='-Wno-error=documentation' \
  -DAPPEND_CPPFLAGS='-DBOOST_MULTI_INDEX_ENABLE_SAFE_MODE' \
 "
 export BITCOIND=bitcoin-node  # Used in functional tests