Remove clang-tidy documentation

clang-tidy is now integrated into CI;  Documenting the "manual" process
for running tidy doesn't provide value these days.  Point to
openbmc-build-scripts as the "recommended" mechanism to run static
analysis.

Tested: Documentation only

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Idac0d29e8976a168355bfa3b863b8600db916f14