Increase string character limits to 40

Increase character limits for the "billing_cycle" and
"app_usage_cycle" strings to 40 characters because the
current limit of 30 characters is not enough for some
translations.

Test: manual
Test: make RunSettingsRoboTests
Bug: 70950124
Change-Id: I2091915ca78786f4b29de211b4635af45cb4946f