Incorrect warning: "@meta block has an unsupported keyword argument: CurrentModule" since v1.2.0

[tkemmer]

Documenter v1.2.0 throws a warning when encountering the CurrentModule keyword in a @meta block,
although the keyword still seem to exist and work as before (and is still shown in the documentation):

┌ Warning: In src/index.md:1-3: `@meta` block has an unsupported keyword argument: CurrentModule
└ @ Documenter ~/.julia/packages/Documenter/ifiMq/src/expander_pipeline.jl:298

The warning occurs for each document containing something like this:

```@meta
CurrentModule = MyModule
...

I think this might be a typo in

https://github.com/JuliaDocs/Documenter.jl/blob/master/src/expander_pipeline.jl#L296

The code checks against :Currentmodule instead of :CurrentModule before generating the warning.

[fredrikekre]

Do you want to make a PR?

[tkemmer]

Sure! I'll prepare one.

[fredrikekre]

Fixed by #2365