fix: E-matching patterns containing ground universe polymorphic patterns in `grind`

This PR ensures `grind` can E-match patterns containing universe
polymorphic ground sub-patterns. For example, given
```
set_option pp.universes true in
attribute [grind?] Id.run_pure
```
the pattern
```
Id.run_pure.{u_1}: [@Id.run.{u_1} #1 (@pure.{u_1, u_1} `[Id.{u_1}] `[Applicative.toPure.{u_1, u_1}] _ #0)]
```
contains two nested universe polymorphic ground patterns
- `Id.{u_1}`
- `Applicative.toPure.{u_1, u_1}`

This kind of pattern is not common, but it occurs in core.