CompatHelper: bump compat for VectorInterface to 0.6 for test env

CompatHelper missed this one because the test env isn't a separately
registered subpackage. Without it, CheckCompatBounds reports an empty
intersection between VectorInterface@0.6.0 and the test workspace
project's compat "0.5".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mtfishman

test/Project.toml

@@ -46,5 +46,5 @@ StableRNGs = "1"
 Suppressor = "0.2"
 TensorOperations = "5.5"
 Test = "1.10"
-VectorInterface = "0.5"
+VectorInterface = "0.5, 0.6"
 Zygote = "0.7"