Merge #18406: test: add executable flag for rpc_estimatefee.py

f0dfac7 test: add executable flag for rpc_estimatefee.py (Sebastian Falbesoner)

Pull request description:

  Again a functional test without executable flag set sneaked in (see e.g. #17806 and #16742 for previous similar PRs, setting the filemode from 644 to 755). Maybe a linter like suggested in #17830 would be worth considering to avoid future (trivial) PRs like this?

ACKs for top commit:
  promag:
    ACK f0dfac7.
  kristapsk:
    ACK f0dfac7

Tree-SHA512: b37c11bdef439aa9d5736c9e0e0bbcc19aff876744f0c4e099ca5c67c9ff1293f1f9140f0d167ea13fee5396ae017aa4a0f1bae4f7aec8fa80b46beb421561c1