INTMDB-133: Vendor removal to include terratest samples

[leofigy]

Description

Context: The provider initially created used the vendor folder. However due to the go modules introduction, there is no longer the need to have the vendor folder. Now we will start introducing terratest so keeping the vendor folder is not an option.

Type of change:

• 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)
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the Terraform contribution guidelines
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code

Further comments

[themantissa]

LGTM! Thank you for this important clean up work!

[coderGo93]

If it works then LGTM!!, thank you