add trailing comma (to follow style guidelines)

src/items/enumerations.md

@@ -168,13 +168,13 @@ It is an error when two variants share the same discriminant.
 ```rust,compile_fail
 enum SharedDiscriminantError {
     SharedA = 1,
-    SharedB = 1
+    SharedB = 1,
 }
 
 enum SharedDiscriminantError2 {
     Zero,       // 0
     One,        // 1
-    OneToo = 1  // 1 (collision with previous!)
+    OneToo = 1, // 1 (collision with previous!)
 }
 ```
 
@@ -185,14 +185,14 @@ It is also an error to have an unspecified discriminant where the previous discr
 #[repr(u8)]
 enum OverflowingDiscriminantError {
     Max = 255,
-    MaxPlusOne // Would be 256, but that overflows the enum.
+    MaxPlusOne, // Would be 256, but that overflows the enum.
 }
 
 #[repr(u8)]
 enum OverflowingDiscriminantError2 {
     MaxMinusOne = 254, // 254
     Max,               // 255
-    MaxPlusOne         // Would be 256, but that overflows the enum.
+    MaxPlusOne,        // Would be 256, but that overflows the enum.
 }
 ```
 
@@ -344,7 +344,7 @@ mac_variant! { E }
 enum E {
     pub U,
     pub(crate) T(u8),
-    pub(super) T { f: String }
+    pub(super) T { f: String },
 }
 ```