Clean up E0323, E0324 and E0325 explanations

Author: GuillaumeGomez

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