Prevent Theme#dump from restricting minimum severity

After Theme#dump is used, all logs with a lower severity than "info"
were not being shown. Removing base::ScopedLogSeverity fixes this
issue. ScopedLogSeverity does not have any purpose in these code blocks
since the dump command is doing the theme logging at a fixed severity.

Bug: 175070283
Test: use debugger to invoke dump and verify that it does not limit
      minimum severity
Change-Id: I4564d119b3672398c6b1d11cd946080cca458218