Fix Typos in scheduled_delay_change.nr and subarray.nr

[teenager-ETH]

Description

This pull request fixes typos in the following files:

1. File: aztec/src/state_vars/shared_mutable/scheduled_delay_change.nr

   • Fixes:
     • Corrected "initally" to "initially" in the description of ScheduledValueChange (Line 5).
     • Corrected "contraints" to "constraints" in a comment within the schedule_change method (Line 58).

2. File: aztec/src/utils/array/subarray.nr

   • Fixes:
     • Corrected "emtpy" to "empty" in a test case description (Line 25).