Move inferred type example to an example block

This text really belonged with the introduction, since it isn't an
explicit rule, but more of a commentary on how the inferred type is
used.

Author: ehuss

src/types/inferred.md

@@ -10,15 +10,15 @@ r[type.inferred.intro]
 The inferred type asks the compiler to infer the type if possible based on the
 surrounding information available.
 
-r[type.inferred.constraint]
-It cannot be used in item signatures.
-
-r[type.inferred.usage]
-It is often used in generic arguments:
+> [!EXAMPLE]
+> The inferred type is often used in generic arguments:
+>
+> ```rust
+> let x: Vec<_> = (0..10).collect();
+> ```
 
-```rust
-let x: Vec<_> = (0..10).collect();
-```
+r[type.inferred.constraint]
+The inferred type cannot be used in item signatures.
 
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