fix(mypy): Fix annotations for 13 cipher algorithms

[dhruvmanila]

Issue: #4052

$ git diff master --name-only  ciphers/a1z26.py  ciphers/affine_cipher.py  ciphers/atbash.py  ciphers/base32.py  ciphers/base85.py  ciphers/beaufort_cipher.py  ciphers/brute_force_caesar_cipher.py  ciphers/cryptomath_module.py  ciphers/decrypt_caesar_with_chi_squared.py  ciphers/diffie.py  ciphers/elgamal_key_generator.py  ciphers/enigma_machine2.py  ciphers/rsa_key_generator.py

Running mypy:

$ git diff master --name-only | xargs -I% mypy --strict % Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file Success: no issues found in 1 source file

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• 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.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.