Fix syntax error in exception handling for greatest_common_divisor

[furygamingind24-art]

Describe your change:

The Bug: Separating multiple exceptions with commas is an obsolete, broken syntax from old versions of Python (Python 2). In modern Python (Python 3), commas inside an except clause are interpreted as an attempt to assign the exception instance to a variable name. Because of this, hitting this line caused the script to crash immediately with a terminal-blocking SyntaxError.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
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• All functions have doctests that pass the automated testing.
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• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[algorithms-keeper]

Closing this pull request as invalid

@furygamingind24-art, this pull request is being closed as none of the checkboxes have been marked. It is important that you go through the checklist and mark the ones relevant to this pull request. Please read the Contributing guidelines.

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