Remove class to fix dark mode readability

What does this MR do?

For #336976 (closed)

This MR makes the class name and execution time fields in the unit test report summary MR widget's modal more readable (especially in dark mode) by removing the text-secondary class from them.

Screenshots

	before 😑	after 😃
normal mode 👓
dark mode 🕶

How to setup and validate locally (strongly suggested)

1. set up unit test reports for a project (or clone this testing project)
2. open a merge request for a branch that changes the results of some unit tests (or for feature-branch in the testing project)
3. ensure pipelines ran for both the base commit and head commit of the merge request's branch
4. navigate to the merge request and expand the unit test report widget
5. click one of the tests in the lists to open the modal

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 properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• 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.