Fix typos in the documentation

Short option "t" was mistranslated to "--test" instead of "--list" in commit
67cad0792b4e6cf22c6cb1b167b149cd176d49f9.

doc/tar.texi

@@ -1464,7 +1464,7 @@ tar: Removing leading '/' from member names
 /home/myself/practice/folk
 /home/myself/practice/jazz
 /home/myself/practice/collection.tar
-$ @kbd{tar --test --file practice.tar}
+$ @kbd{tar --list --file practice.tar}
 home/myself/practice/
 home/myself/practice/blues
 home/myself/practice/folk
@@ -1495,7 +1495,7 @@ home/myself/practice/blues
 home/myself/practice/folk
 home/myself/practice/jazz
 home/myself/practice/collection.tar
-$ @kbd{tar --test --file practice.tar}
+$ @kbd{tar --list --file practice.tar}
 home/myself/practice/
 home/myself/practice/blues
 home/myself/practice/folk