docs: perf: Fix build warning of hisi-pcie-pmu.rst

docs: perf: Fix build warning of hisi-pcie-pmu.rst

`make htmldocs SPHINXDIRS="admin-guide"` shows below warnings:
Documentation/admin-guide/perf/hisi-pcie-pmu.rst:48: ERROR: Unexpected indentation.
Documentation/admin-guide/perf/hisi-pcie-pmu.rst:49: WARNING: Block quote ends without a blank line; unexpected unindent.

Fix this.

Closes: https://lore.kernel.org/lkml/20231011172250.5a6498e5@canb.auug.org.au/
Fixes: 89a032923d4b ("docs: perf: Update usage for target filter of hisi-pcie-pmu")
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240305122517.12179-1-yangyicong@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>