fix(docx): OMML conversion failures for unsupported limit functions (#3359)

* fix(docx): handle unsupported limit functions gracefully in OMML conversion

Replace RuntimeError with graceful fallback for unknown limit functions in do_limlow().
Add argmax and argmin to LIM_FUNC dictionary for proper LaTeX rendering.
Fixes conversion failures when Word documents contain mathematical operators
not previously supported in the limit function dictionary.

Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>

* test(docx): regenerate ground truth files

Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>

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Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>