SF: Remove static screen stats

This section of dumpsys seemingly hasn't been used since 2015, and
is inaccurate considering drift away from the ideal VSYNC period,
refresh rate switching, and multi-display.

Bug: 241285477
Test: m libsurfaceflinger_unittest
Change-Id: Icc96fbdcfc070d61164c7dfdfe64d112eb19f1b0