Fix certificate manager UI (take 2)

Change layout height so it does not obscure the floating
action buttons at the bottom.

Bug: 349518143
Flag: EXEMPT bug fix
Test: manual CTS Verifier run
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0922f282d8a0eb8ec818323485ea2bdb196c8185)
Merged-In: Iaf82b2e6343790bbed9508a5dae9a66566760cac
Change-Id: Iaf82b2e6343790bbed9508a5dae9a66566760cac