CI: Remove "Total errors found" line from cpplint output

The newly built Docker image must have gotten a newer version of cpplint
which prints a total error count at the end. We need to remove this line
or the error counts will be flagged as a diff in the linter output.
26 jobs for msvc-code-changes in 6 minutes and 35 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Source Check
passed #234001
cppcheck

00:01:00

passed #234002
cpplint

00:01:17

passed #234003
eslint

00:01:02

passed #234000
fedora

00:03:05

 
  Test
passed #234007
no_graphics

00:02:45

passed #234008
no_profiler

00:03:15

passed #234009
no_readline

00:03:19

passed #234004
sanitizer_gcc

00:03:29

passed #234005
with_logging

00:03:23

passed #234006
with_systemtap

00:03:15

 
  Manual
manual #234023
allowed to fail manual
armv8
manual #234010
allowed to fail manual
codequality
manual #234011
allowed to fail manual
code_statistics
manual #234025
allowed to fail manual
coverage
manual #234013
allowed to fail manual
fedora_gcc
manual #234019
allowed to fail manual
flatpak
manual #234014
allowed to fail manual
installed_tests
manual #234017
allowed to fail manual
lts
manual #234024
allowed to fail manual
ppc64le
manual #234012
allowed to fail manual
sanitizer_clang
manual #234016
allowed to fail manual
ubuntu_clang
manual #234015
allowed to fail manual
ubuntu_gcc
manual #234018
allowed to fail manual
valgrind
manual #234022
allowed to fail manual
zeal_11
manual #234020
allowed to fail manual
zeal_2
manual #234021
allowed to fail manual
zeal_4