Fix source of flakiness for lsp/completion test

Summary:
I noticed that {D17584973} failed this test. I think it was a source of flakiness. Most of the test cases look like

1. Add `jsx.js` (which has syntax errors)
2. Start the lsp server and server
3. Send a completion request
4. Assert the response matches.

When the lsp starts up, it will see the syntax errors and send the `textDocument/publishDiagnostics` message to the client. Usually this happens between steps 2 and 3. But if it happens after 3 then the step 4 assertion would fail like this:

```

+ textDocument/publishDiagnostics,textDocument/completion{"isIncomplete":false,"items":[{"label":"a","kind":6,"detail":"number","inlineDetail":"number","insertTextFormat":1}]}
- textDocument/completion{"isIncomplete":false,"items":[{"label":"a","kind":6,"detail":"number","inlineDetail":"number","insertTextFormat":1}]}
```

(Full logs: P113545680)

Easy fix. Just ignore those messages

Reviewed By: nmote

Differential Revision: D17602294

fbshipit-source-id: 7c6f2a7ae84f5d3caffae90fdaacc0e57ea46775

v0.108.0

Reviewed By: gabelevi

Differential Revision: D17464010

fbshipit-source-id: e5d1c97433ac48debde4fe746cc339de4e434d08

v0.107.0

Reviewed By: mroch

Differential Revision: D17191133

fbshipit-source-id: 0cb3b789ac030c24144db8ec054a50abaa62fe72

v0.106.3

Reviewed By: jbrown215

Differential Revision: D17114108

fbshipit-source-id: 349e2a00ece145901b361a7820599556c28d93c0

v0.106.2

Summary: (Note: this ignores all push blocking failures!)

Reviewed By: mroch

Differential Revision: D17051834

fbshipit-source-id: 91b5a0909793229e789435f2452eb816a0b16b88

v0.106.1

Reviewed By: jbrown215

Differential Revision: D16996727

fbshipit-source-id: 40a62d79a98d261e0ef578ecd6390cc788a7400c

v0.106.0

Reviewed By: jbrown215

Differential Revision: D16949952

fbshipit-source-id: 2415fc2f0605c80c9acddd1ebaf0fd36d6257d5d

v0.105.2

Reviewed By: gabelevi

Differential Revision: D16773406

fbshipit-source-id: 945fd9cb0195fdad5644e0bcd70078f3859f0898

v0.105.0

Summary: (Note: this ignores all push blocking failures!)

Reviewed By: mroch

Differential Revision: D16730323

fbshipit-source-id: fa671fe493b7bc5b14206f23dc932617a1a8db81

v0.104.0

Reviewed By: jbrown215

Differential Revision: D16501865

fbshipit-source-id: 4fb8ade73c7d69d289101dbe83036b7cb7deb6f0