Remove unused variables from test files

tests/t08-tag.c

@@ -121,11 +121,8 @@ END_TEST
 
 BEGIN_TEST(write1, "write a tag to the repository which points to an unknown oid should fail")
 	git_repository *repo;
-	git_tag *tag;
 	git_oid target_id, tag_id;
 	const git_signature *tagger;
-	git_reference *ref_tag;
-	git_object *zombie;
 
 	must_pass(git_repository_open(&repo, REPOSITORY_FOLDER));
 

tests/t09-tree.c

@@ -132,7 +132,6 @@ END_TEST
 
 BEGIN_TEST(write2, "write a tree from a memory")
 	git_repository *repo;
-	git_index *index;
 	git_treebuilder *builder;
 	git_tree *tree;
 	git_oid id;