in_docker: update function pointer signatures with correct args for C23

[nuclearpidgeon]

see: https://gcc.gnu.org/gcc-15/porting_to.html#c23-fn-decls-without-parameters

Fixes the same GCC15 build error as #10489 but for the Docker plugin where it was also a problem.

Docker plugin split from #10476

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license

[patrick-stephens]

Just to ensure no legacy targets are affected I think we need to trigger the packaging builds as well - weird stuff can happen on the older compilers.

[nuclearpidgeon]

In theory this change should just be adding specific typing that was already at play where these types are all used, but yeah, worth doing

[cosmo0920]

In theory this change should just be adding specific typing that was already at play where these types are all used, but yeah, worth doing

Especially for CentOS 7, we need to run off the packaging task.