commands/command_ext.go: translate ext header only

In commit 1ddc2f2 of
PR git-lfs#4781 text translation support was added for the
"git lfs ext" command and a multi-line message was
concatenated.  However, the latter part of this text should
be fixed for all users, since it displays a listing of
the extension's settings values using defined terms.

We therefore separate the first line of the message and
let that be translated, as it contains the language-specific
header text.

commands/command_ext.go

@@ -37,10 +37,10 @@ func printAllExts() {
 }
 
 func printExt(ext config.Extension) {
-	Print(tr.Tr.Get(`Extension: %s
-    clean = %s
+	Print(tr.Tr.Get("Extension: %s", ext.Name))
+	Print(`    clean = %s
     smudge = %s
-    priority = %d`, ext.Name, ext.Clean, ext.Smudge, ext.Priority))
+    priority = %d`, ext.Clean, ext.Smudge, ext.Priority)
 }
 
 func init() {