Truth: Move export to runtime_deps

There is no good reason why depending on //lib/truth should free
downstream libraries from needing a direct dep on //lib/guava or
//lib/junit. Exporting the deps was probably just oversight, since the
distinction between exports and runtime_deps in WORKSPACE is not
obvious, and there are probably other bad examples.

Change-Id: I1530106d642167eaa25222cc95c3996478728e15

java/com/google/gerrit/acceptance/BUILD

@@ -76,6 +76,7 @@ java_library2(
         "//java/com/google/gerrit/server/group/testing",
         "//java/com/google/gerrit/server/project/testing:project-test-util",
         "//java/com/google/gerrit/testing:gerrit-test-util",
+        "//lib:guava",
         "//lib:jimfs",
         "//lib/auto:auto-value",
         "//lib/auto:auto-value-annotations",