[ty] Fix subtyping for dynamic specializations (#20592)

## Summary

Fixes a bug observed by @AlexWaygood where `C[Any] <: C[object]` should
hold for a class that is covariant in its type parameter (and similar
subtyping relations involving dynamic types for other variance
configurations).

## Test Plan

New and updated Markdown tests

crates/ty_python_semantic/src/types/generics.rs

@@ -841,18 +841,6 @@ impl<'db> Specialization<'db> {
             .zip(self.types(db))
             .zip(other.types(db))
         {
-            // As an optimization, we can return early if either type is dynamic, unless
-            // we're dealing with a top or bottom materialization.
-            if other_materialization_kind.is_none()
-                && self_materialization_kind.is_none()
-                && (self_type.is_dynamic() || other_type.is_dynamic())
-            {
-                match relation {
-                    TypeRelation::Assignability => continue,
-                    TypeRelation::Subtyping => return ConstraintSet::from(false),
-                }
-            }
-
             // Subtyping/assignability of each type in the specialization depends on the variance
             // of the corresponding typevar:
             //   - covariant: verify that self_type <: other_type