No need to show release tag name in `release show <TAG>` output

Since TAG is provided as argument, the user already knows the tag name
and there's no need to include it (rather clumsily) in the output.

commands/release.go

@@ -172,7 +172,7 @@ func showRelease(cmd *Command, args *Args) {
 
 		body := strings.TrimSpace(release.Body)
 
-		ui.Printf("%s (%s)\n", release.Name, release.TagName)
+		ui.Println(release.Name)
 		if body != "" {
 			ui.Printf("\n%s\n", body)
 		}

features/release.feature

@@ -93,7 +93,7 @@ MARKDOWN
     When I successfully run `hub release show v1.2.0`
     Then the output should contain exactly:
       """
-      will_paginate 1.2.0 (v1.2.0)
+      will_paginate 1.2.0
 
       ### Hello to my release
 
@@ -129,7 +129,7 @@ MARKDOWN
     When I successfully run `hub release show v1.2.0 --show-downloads`
     Then the output should contain exactly:
       """
-      will_paginate 1.2.0 (v1.2.0)
+      will_paginate 1.2.0
 
       ### Hello to my release