Remove shebang in build.lua about l3build

[josephwright]

Sorted

[muzimuzhi]

texlua build.lua ... is still supported and used when testing l3build itself, for example in workflow files in current repository.

l3build/.github/workflows/main.yaml

Lines 26 to 27 in bbe66f5

	- name: Run l3build
	run: texlua l3build.lua ctan -H --show-log-on-error

l3build/.github/workflows/deploy.yaml

Lines 28 to 29 in bbe66f5

	- name: Run l3build
	run: texlua l3build.lua ctan -H --show-log-on-error

So what @jlaurens meant "dropped" was usage ./build.lua ...?

[josephwright]

texlua build.lua ... is still supported and used when testing l3build itself, for example in workflow files in current repository.

Well, texlua ./l3build.lua, and as that's purely for developers of l3build, I think it's a very niche case :)