Open addon purchase in the same window

What does this MR do?

Update Buy additional minutes (addons purchase flow) link to open in the same page.

Closes #338237 (closed)

Screenshots or Screencasts (strongly suggested)

How to setup and validate locally (strongly suggested)

Make sure that you have any license activated

1. Navigate to /dashboard/groups
2. Choose a group with free subscription
3. In the left menu choose Settings -> Usage quotas
4. Click Buy additional minutes

or

1. Visit groups/<your-group>/-/usage_quotas#pipelines-quota-tab

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.