Remove defunct unused AGASC_FILE from observations

[jeanconn]

Description

Remove defunct unused AGASC_FILE from observations

Interface impacts

Testing

Unit tests

• Mac

(ska3-flight-2026.1) flame:kadi jean$ git rev-parse HEAD
3f3e16ba131a4a121899ccc69bd9a167edccacc5
(ska3-flight-2026.1) flame:kadi jean$ pytest
================================================================================ test session starts =================================================================================
platform darwin -- Python 3.13.11, pytest-9.0.2, pluggy-1.6.0
rootdir: /Users/jean/git
configfile: pytest.ini
plugins: anyio-4.12.1, timeout-2.4.0
collected 313 items                                                                                                                                                                  

kadi/commands/tests/test_commands.py ...............................................................s..............................                                            [ 30%]
kadi/commands/tests/test_commands_v2.py ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss                                               [ 58%]
kadi/commands/tests/test_filter_events.py ..                                                                                                                                   [ 58%]
kadi/commands/tests/test_states.py ...............................................x..........................                                                                  [ 82%]
kadi/commands/tests/test_validate.py ......................                                                                                                                    [ 89%]
kadi/tests/test_events.py ..........                                                                                                                                           [ 92%]
kadi/tests/test_occweb.py .......................                                                                                                                              [100%]

=============================================================== 223 passed, 89 skipped, 1 xfailed in 189.20s (0:03:09)

Independent check of unit tests by [REVIEWER NAME]

• [PLATFORM]:

Functional tests

No functional testing.