perf ui browsers: Remove help messages about use of right and arrow keys

perf ui browsers: Remove help messages about use of right and arrow keys

They were repurposed for horizontal scrolling, so use just ENTER/ESC in
the help messages.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 3e4ff5f31b4b ("perf hists browser: Implement horizontal scrolling")
Link: http://lkml.kernel.org/n/tip-n5ar4qg8fs12ax4vhr3rxhxj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>