User's Guide: Delete "Building the CLM tools*" sections.

[samsrabin]

Description of changes

Deletes the User's Guide page with the "Building the CLM tools" and "Building the CLM tools that use the CIME configure/build system" sections. Its contents are not really helpful to begin with, and they're no longer needed anyway:

• As that page notes, gen_domain needed anymore with NUOPC.
• I have a PR open, User's Guide: Update "Comparing history files" page #3987, that will describe how to build and use cprnc.
• mksurfdata_esmf is a special enough tool that I don't think it belongs in the User's Guide, and anyway there's no useful information about it here.
• We have a separate "Adding new resolutions" page.

Specific notes

Contributors other than yourself, if any:

• None

CTSM issues resolved or otherwise addressed, if any:

• None

Any user interface changes (namelist or namelist defaults changes)? No

Testing planned or performed, if any:

• Local doc build

Requirements before merge:

• I have followed the CTSM contribution guidelines.

[samsrabin]

@slevis-lmwg This is relevant to you, since you're assigned to review the User's Guide section where this is (see #3882). Would you mind reviewing this PR?