[Phone Hub] Update Learn More pill button type

Previously, the Learn More pill button was using kFloatingWithoutIcon.
During the Jelly migration, this was not updated as the appropriate Type
(kSecondaryWithoutIcon) had contrast ratio issues. That has since been
resolved and we are now migrating this pill button.

Before Screenshots
BT Disabled: https://screenshot.googleplex.com/7gEXTCmHfE96yDj.png
Disconnected: https://screenshot.googleplex.com/BAPfZH52g2rp5z2.png

After Screenshots
BT Disabled: https://screenshot.googleplex.com/AwPg5TrKZusvLFu.png
Disconnectd: https://screenshot.googleplex.com/4jEPJb4ijQyTkE7.png

Test: manually verified, provided screenshots
Bug: b/281844561
Change-Id: I037ee6753b34dedc6409a5838941227574720be8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5234562
Auto-Submit: Crisrael Lucero <crisrael@google.com>
Reviewed-by: Jon Mann <jonmann@chromium.org>
Commit-Queue: Crisrael Lucero <crisrael@google.com>
Commit-Queue: Jon Mann <jonmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1251655}