Made changes in spellings of the convert_number_to_letter.c file

[jayaganeshkumar]

Description

@pratik-choudhari A comprehensive description about the Pull Request

Reference Issue number #238

issue_no must refer to the issue related to this PR, visit here

Type of change

Corrected some of the spelling mistakes in the files merged with PR #335

Choosing one or more options from the following as per the nature of your Pull request. NOTE: Check boxes using [x]

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Documentation Update

Checklist:

• [ ] I have named my files and folder, according to this project's guidelines.
• [ ] My code follows the style guidelines of this project.
• [ ] My Pull Request has a descriptive title. (not a vague title like Update index.md)
• [ ] I have commented on my code, particularly in hard-to-understand areas.
• [ ] I have created a helpful and easy to understand README.md, with problem description and my name.
• [ ] I have included a requirements.txt file (if external libraries are required.)
• [X] My changes do not produce any warnings.
• [X] I have starred this repository.
• [ ] I have added a working sample/screenshot of the script.
• [ ] I have checked for trailing spaces in file names and none have them.