docs: improve language in generics section (#2884)

I asked Gemini to review the English for inconsistencies and grammar
mistakes. This is the result and I hope it's useful!

As a non-native speaker, it is hard for me to evaluate the finer
details, so let me know if you would like to see changes (or even
better: make them directly in the PR with the suggestion function).

src/generics/dyn-trait.md

@@ -60,7 +60,7 @@ fn main() {
   instance of the function for each different type that the generic is
   instantiated with. This means that calling a trait method from within a
   generic function still uses static dispatch, as the compiler has full type
-  information and can resolve which type's trait implementation to use.
+  information and can resolve that type's trait implementation to use.
 
 - When using `dyn Trait`, it instead uses dynamic dispatch through a
   [virtual method table][vtable] (vtable). This means that there's a single

src/generics/generic-data.md

@@ -44,7 +44,7 @@ fn main() {
 
 <details>
 
-- _Q:_ Why `L` is specified twice in `impl<L: Logger> .. VerbosityFilter<L>`?
+- _Q:_ Why is `L` specified twice in `impl<L: Logger> .. VerbosityFilter<L>`?
   Isn't that redundant?
   - This is because it is a generic implementation section for generic type.
     They are independently generic.

src/generics/impl-trait.md

@@ -30,7 +30,7 @@ fn main() {
 
 <details>
 
-`impl Trait` allows you to work with types which you cannot name. The meaning of
+`impl Trait` allows you to work with types that you cannot name. The meaning of
 `impl Trait` is a bit different in the different positions.
 
 - For a parameter, `impl Trait` is like an anonymous generic parameter with a