conda: disable '--update-deps' to work around buggy libffi(?)

[jsiirola]

Fixes # .

Summary/Motivation:

Windows conda builds are currently broken because running conda with --update-deps causes libffi to be updated which results in

ImportError: DLL load failed while importing _ctypes: The specified module could not be found.

when trying to install conda packages.

Changes proposed in this PR:

• remove --update-deps from conda install of conda-libmamba-solver

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