Documentation bug: `MainInclude`

[nsajko]

Base.MainInclude.include was deleted from Base.MainInclude for v1.11, even though it's documented. The explanation is that Base.MainInclude is intended as a mere implementation detail: #54057. In that case remaining references to Base.MainInclude should be removed from the docs, to prevent further confusion and breakage. ans and err are still documented as belonging to Base.MainInclude: https://docs.julialang.org/en/v1.12-dev/base/base/#Base.MainInclude.ans