fix the inconsistent casing of meta files

[hyounesy]

Proposed change(s)

While renaming the source files in #126 , git had not detected the change in the casing of the meta files. Resulting in warnings like the following in Unity Editor when making a fresh checkout:

Asset file 'Packages/com.unity.robotics.urdf-importer/Editor/MenuItems/CompareUrdf.cs.meta' and meta file 'Packages/com.unity.robotics.urdf-importer/Editor/MenuItems/CompareURDF.cs.meta' has inconsistent casing.

This PR is to fix the casing for the four affected files.

Useful links (GitHub issues, JIRA tickets, forum threads, etc.)

#126

Types of change(s)

• Bug fix
• New feature
• Code refactor
• Documentation update
• Other (please describe)

Testing and Verification

NA

Test Configuration:

• Unity Version: Unity 2020.3.13f1
• Unity machine OS + version: macos Catalina 10.15.7

Checklist

• Ensured this PR is up-to-date with the dev branch
• Created this PR to target the dev branch
• Followed the style guidelines as described in the Contribution Guidelines
• Added tests that prove my fix is effective or that my feature works
• Increased the test coverage criteria by 3%
• Updated the Changelog and described changes in the Unreleased section
• Updated the documentation as appropriate