Remove HashTreeInfo from verity_utils.py

We are removing VB related functionalities from release tools. This
change removes the hashtreeinfo and generator in verity_utils.py. It
also clears the function args using it.

Bug: 241044073
Test: atest under build/make
Change-Id: Icc298256be6917ffbd40cf4735f8e8092b541c9f
diff --git a/tools/releasetools/test_verity_utils.py b/tools/releasetools/test_verity_utils.py
index ada70e6..4a0ff09 100644
--- a/tools/releasetools/test_verity_utils.py
+++ b/tools/releasetools/test_verity_utils.py
@@ -27,8 +27,7 @@
 from test_utils import (
     get_testdata_dir, ReleaseToolsTestCase, SkipIfExternalToolsUnavailable)
 from verity_utils import (
-    CalculateVbmetaDigest, CreateHashtreeInfoGenerator,
-    CreateVerityImageBuilder, HashtreeInfo)
+    CalculateVbmetaDigest, CreateVerityImageBuilder)
 
 BLOCK_SIZE = common.BLOCK_SIZE