Vendor field is not populated automatically in Add backup dialog

*User Impact:*

User is not able to see Vendor type at Add backup dialog

*Steps to Reproduce:*
#1 ADD MySQL / MongoDB via pmm-admin under monitoring
#2 navigate to /graph/backup/inventory
#3 click on Add in the right corner

#4 Backup on demand modal will be open

#6 select Service which you've added at step 1 at service field.

#7 at this point Vendor should be field based on service vendor

*Actual Result:*

Vendor Type is empty

*Expected Result:*
Vendor should be populated from service like f.e MySQL | MongoDB etc