Revert "Allow modification of ro.telephony.default_network"

This reverts commit c3568c47b0b568edc784bb9ea830454342836971.

The change was uploaded only to pi-dev but landed on AOSP/master
via pi-dev-plus-aosp. The existence of this change in AOSP/master causes
downstream merge conflicts (e.g. internal master).

Reverting the P-only change in AOSP/master.

Bug: 110626665
Test: N/A
Change-Id: I24342db0fa754ec97746900dd4d0791ade509095
1 file changed