Update freezing notes.

Since it was a big problem for little gain, we are reverting back to the
old practice of waiting to freeze interfaces for release.
vts_treble_vintf_*_test no longer checks hashes in non-release branches.

Bug: 144366823
Test: N/A
Change-Id: I147025ffed053bc583055fbc4f39d9823e793c22
diff --git a/current.txt b/current.txt
index becbf9b..4614b0d 100644
--- a/current.txt
+++ b/current.txt
@@ -654,4 +654,5 @@
 # ABI preserving changes to HALs during Android S
 
 # HALs released in Android S
+# NOTE: waiting to freeze HALs until later in the release
 # NOTE: new HALs are recommended to be in AIDL