Fix missed conservative -> prognostic rename in docs.

[charleskawczynski]

Description

Fix some missed name change from conservative to prognostic in docs.

I have

• Written and run all necessary tests with CLIMA by including tests/runtests.jl
• Followed all necessary style guidelines and run julia .dev/climaformat.jl .
• Updated the documentation to reflect changes from this PR.

For review by CLIMA developers

• There are no open pull requests for this already
• CLIMA developers with relevant expertise have been assigned to review this submission
• The code conforms to the style guidelines and has consistent naming conventions. julia .dev/format.jl has been run in a separate commit.
• This code does what it is technically intended to do (all numerics make sense physically and/or computationally)

[charleskawczynski]

bors r+

[bors]

Build succeeded:

• ci/slurmci
• docs-build
• format
• test-os (macos-latest)
• test-os (ubuntu-latest)
• test-os (windows-latest)