Fix function name on docs: perform_ocr_batch

[pedroeagle]

Description

When I read the docs to use the library I got some problems with function name. 'GoogleOCRApplication' object has no attribute 'perform_batch_ocr

Motivation and Context

I just read the library code and saw that, actually the function name is perform_ocr_batch.

How has this been tested?

I just changed my function naming call and the problem was fixed. It was just a doc outdated.

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.

[hrishikeshrt]

Thank you.