Merge bitcoin#20346: script: modify security-check.py to use "==" ins…

…tead of "is" for literal comparison

b6121ed swapped "is" for "==" in literal comparison (Tyler Chambers)

Pull request description:

  In Python 3.8+ literal comparisons using "is" instead of "==" produce a SyntaxWarning [source](https://docs.python.org/3.8/whatsnew/3.8.html#changes-in-python-behavior).

  I checked the entire devtools directory, this seems to be the only occurrence.

  This is a small fix, but removes the SyntaxWarning.
  Fixes: bitcoin#20338

ACKs for top commit:
  hebasto:
    re-ACK b6121ed, only squashed since my [previous](bitcoin#20346 (review)) review.
  practicalswift:
    re-ACK b6121ed: patch still looks correct
  theStack:
    utACK b6121ed

Tree-SHA512: 82a43495d6552fbaa3b02b58f0930b049d27aa937fe44b47714e3c059f844cc494de20674557371cbccf24fb8873ecb7376fb965ae326847eed2b855ed2d59c6

test/lint/lint-python.sh

@@ -55,6 +55,7 @@ enabled=(
     F621 # too many expressions in an assignment with star-unpacking
     F622 # two or more starred expressions in an assignment (a, *b, *c = d)
     F631 # assertion test is a tuple, which are always True
+    F632 # use ==/!= to compare str, bytes, and int literals
     F701 # a break statement outside of a while or for loop
     F702 # a continue statement outside of a while or for loop
     F703 # a continue statement in a finally block in a loop