Bug 2021137 - Fix Loop in Nimbus Gecko Preferences Project

[ohall-m]

Using self.end_initialize(db, writer, &mut state)?; instead of writer.commit()?; caused a loop with Android of: register_previous_gecko_pref_states ->
commit_and_update ->
map_gecko_prefs_to_enrollment_slugs_and_update_store -> set_gecko_prefs_state ->
setGeckoPrefsState->
nimbusApi!!.registerPreviousGeckoPrefStates ->

This patch adjusts it to a simple commit.

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