android_filesystem_config: Remove AID_QCOM_DIAG entry

The /dev/diag node is switching to using oem_2901 group
permissions for access control. Hence the patch removes
AID_QCOM_DIAG entry.

@Discard: /dev/diag node permissions changed to oem_2901
so no need of AID_QCOM_DIAG
@topic:QC_Value_Added_Features
CRs-Fixed: 2071439
Change-Id: I7d0e8f5ed18707b5a9908cb6aef3778b6e28ecc6