perf/x86/intel/uncore: Remove extra double quote mark

The third argument in INTEL_UNCORE_FR_EVENT_DESC() is subject to
__stringify(), and the extra double quote marks can result in the
expansion "3.814697266e-6" in the sysfs knobs, instead of
3.814697266e-6.

This is incorrect, though it may still work for perf, e.g.
perf stat -e uncore_iio_free_running_0/bw_in_port0/

Fixes: d8987048f665 ("perf/x86/intel/uncore: Support IIO free-running counters on DMR")
Closes: https://lore.kernel.org/all/20251231224233.113839-1-zide.chen@intel.com/
Reported-by: Chun-Tse Shao <ctshao@google.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chun-Tse Shao <ctshao@google.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://patch.msgid.link/20260313174050.171704-5-zide.chen@intel.com