PlzNavigate: fix 2 SitePerProcessBrowserTests that were using the pending RFH

This Cl fixes 2 SitePerProcessBrowserTests that were using the pending
RenderFrameHost. When BrowserSideNavigation is enabled, they now use the
speculative RenderFrameHost.

BUG=475027

Review URL: https://codereview.chromium.org/1722673003

Cr-Commit-Position: refs/heads/master@{#377855}
2 files changed