Clean up E0323, E0324, E0325 and E0326 explanations

src/librustc_error_codes/error_codes/E0323.md

@@ -1,4 +1,5 @@
 An associated const was implemented when another trait item was expected.
+
 Erroneous code example:
 
 ```compile_fail,E0323

src/librustc_error_codes/error_codes/E0324.md

@@ -1,5 +1,6 @@
-A method was implemented when another trait item was expected. Erroneous
-code example:
+A method was implemented when another trait item was expected.
+
+Erroneous code example:
 
 ```compile_fail,E0324
 struct Bar;

src/librustc_error_codes/error_codes/E0325.md

@@ -1,4 +1,5 @@
 An associated type was implemented when another trait item was expected.
+
 Erroneous code example:
 
 ```compile_fail,E0325

src/librustc_error_codes/error_codes/E0326.md

@@ -1,7 +1,6 @@
-The types of any associated constants in a trait implementation must match the
-types in the trait definition. This error indicates that there was a mismatch.
+An implementation of a trait doesn't match the type contraint.
 
-Here's an example of this error:
+Erroneous code example:
 
 ```compile_fail,E0326
 trait Foo {
@@ -14,3 +13,6 @@ impl Foo for Bar {
     const BAR: u32 = 5; // error, expected bool, found u32
 }
 ```
+
+The types of any associated constants in a trait implementation must match the
+types in the trait definition.