perf evlist: Remove group option.

The group option predates grouping events using curly braces added in
commit 89efb029

 ("perf tools: Add support to parse event group
syntax").

The --group option was retained for legacy support (in August
2012) but keeping it adds complexity.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Eelco Chaudron <echaudro@redhat.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shaomin Deng <dengshaomin@cdjrlc.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Timothy Hayes <timothy.hayes@arm.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20221213232651.1269909-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>