Fix: Added missing opts argument in MGF test cases

[akash8843]

Resolves #{{Address commit comments (commit 276f077) #5710}}.

Description

This pull request fixes missing opts argument in MGF test cases for the triangular distribution. Added proper test cases to handle edge scenarios and ensure valid function outputs.

Related Issues

Closes #<#5710> (Address commit comments (commit 276f077))

Checklist

• Added necessary test cases
• Verified code passes all tests

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/geometric/cdf	$\color{green}291/291$ $\color{green}+100.00\%$	$\color{green}27/27$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}291/291$ $\color{green}+100.00\%$
stats/base/dists/triangular/mgf	$\color{red}344/348$ $\color{green}+98.85\%$	$\color{red}25/27$ $\color{green}+92.59\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{red}344/348$ $\color{green}+98.85\%$

The above coverage report was generated for the changes in this PR.