arm64: defconfig: don't set CONFIG_ACPI_APEI_PCIEAER

Since 8c8ff55b

 ("PCI/AER: Don't select CONFIG_PCIEAER by default"), PCIe
Advanced Error Reporting isn't enabled by default.. As this means just
enabling CONFIG_CPI_APEI_PCIEAR does not have an effect, remove it from
the defconfig for clarity.

Signed-off-by: Ross Burton <ross.burton@arm.com>