Fix conversation minimal HUN getting clipped too early

We were adding an unnecessary margin to conversation minimal HUNs,
that's already being added in the layout.

Fix: 430893680
Test: manual
Flag: android.app.notifications_redesign_templates
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7e57326d890fe07a0fc6840d589389749d19d149)
Merged-In: I2cac6f7aff18b9dbfda9e05686fa9fe524cbf424
Change-Id: I2cac6f7aff18b9dbfda9e05686fa9fe524cbf424