replace `require` with `require_once` in `entryPoint.php`

[JoshMcCullough]

Description

I am not a "PHP Guy", so this could be wrong. However, it fixes error messages such as:

PHP Fatal error: Cannot declare class TemplateText, because the name is already in use

Same with LanguageManager.php and VardefManager.php, and likely but not confirmed, TemplateText.php.

Motivation and Context

I noticed the error while authenticating via the API, when the server returned 500.

How To Test This

Execute the below command and verify that the above error message does not appear in the log.

curl --location --request GET 'localhost/service/v4_1/rest.php' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'method=login' \
--data-urlencode 'input_type=JSON' \
--data-urlencode 'response_type=JSON' \
--data-urlencode 'rest_data={"user_auth":{"user_name":"admin","password":"password"},"application_name":"test"}'

Types of changes

• [ x ] 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 change)

Final checklist

• [ x ] My code follows the code style of this project found here.
• [ _ ] My change requires a change to the documentation.
• [ x ] I have read the How to Contribute guidelines.

[SuiteBot]

All committers have signed the CLA.

[JoshMcCullough]

Can we get this simple fix merged soon, please?