[copyright] add MIT License copyright header to remaining Python files

[isle2983]

The edit history on these three files are from users:

contrib/devtools/security-check.py (@ChoHag, @laanwj, @theuni, @calebogden)
contrib/devtools/test-security-check.py (@ChoHag, @laanwj)
share/qt/extract_strings_qt.py (@ChoHag, @MitchellCash, @laanwj, @luke-jr, @brandondahler, Phillip Kaufmann, @theuni)

As per the threads for PR #7300 and #8676, there are ACKs to add these headers
from all but Philip Kaufmann and @ChoHag.

The specific edits:

@ChoHag edited security-check.py in 7b01ce2 and 873e81f
@ChoHag edited test-security-check.py in 873e81f
@ChoHag edited extract_strings_qt.py in 873e81f
Philip Kaufmann edited extract_strings_qt.py in 01cbaeb

I will make an effort to reach out via email.

[isle2983]

It has been a couple days, and I haven't heard back. For the record, the emails that were sent to the addresses listed in the git commits:

https://gist.github.com/isle2983/1f4bce2eb202553c3e209be5b6606745
https://gist.github.com/isle2983/e84b22121854c56cfe3829f986bcfdf6

If I hear anything, I will post it here ASAP.

The edits to these files are are all 1-liners (7b01ce2, 873e81f, 01cbaeb). IANAL, but I think it is fairly reasonable to conclude that there aren't any IP violations contained in those edits.

I will leave it up to the project leads for whether this is appropriate to merge.

[laanwj]

Thanks for trying to organize this. As the original author of security-check.py and test-security-check.sh I think my agreement to add an copyright header is most important, as I should have done that in the first place. The other changes, apart from @theuni's, who also agrees with the MIT license, are just typo and comment fixes so I'm fine with doing this without their agreement.

Same for share/qt/extract_strings_qt.py - except that @luke-jr significantly contributed there too, but he agreed to in previous related pulls. So let's just move on here.