Update namespace for `enable_pcc_framework_support` flag.

The namespace for the `enable_pcc_framework_support` flag is changed from "private_compute_core" to "private_compute". private_compute_core namespace was used by legacy flagging and was requested to use new namespace to not interfere with the old name space.

Test: N/A
Bug: 430201829
Flag: android.app.privatecompute.flags.enable_pcc_framework_support
Change-Id: Ie1f192c3a2088a1f1cbc09283bc545363bac217b