Filling as a good first bug to learn workflows.

, ""); at the end of static_assert is useless

https://searchfox.org/mozilla-central/source/mfbt/Poison.cpp#126-127
Please fix the two occurrences

As the change is trivial, it is just to learn how to contribute to Firefox.

Found by http://clang.llvm.org/extra/clang-tidy/checks/modernize-unary-static-assert.html

Tutorial to contribute:
https://firefox-source-docs.mozilla.org/tools/docs/contribute/how_to_contribute_firefox.html

Please don't ask for the bug to be assigned. It will be automatically assigned to the first patch.

Also, please only work on two max of such bugs.

I believe this was done since a 2nd param was mandatory before C++17. Instead of dropping it altogether, shouldn't it be replaced with a relevant message? Not sure if the check was already made in one of the callers in the stack frame?

The seconds argument for diagnostic message is optional from C++17

https://hg.mozilla.org/mozilla-central/rev/7141fcbeef99