Remove executable file mode from some functional tests

Summary: test_runner is used to run tests. These tests now match the file mode of other functional tests.

Test Plan:

ninja check-functional

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, PiRK

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17287