Edit: Fix leaky XML tags

[umpox]

Description

Reported here: https://sourcegraph.slack.com/archives/C05AGQYD528/p1700227846587329

Fixups can sometimes leak tags:

• When little context is provided, so Cody gets confused about the task
• Due to multiple tags being used, Cody sometimes thinks they are to be used in the response.

Test plan

Test creating fixups.

Primarily test creating fixups on code actions, where we provide the least context

[abeatrix]

I tried to run a code action and it's stuck in cody is working even when we get the response back 🤔

[abeatrix]

Restarted work. The job still contains the leaked tags though:

This is the file I run the Code Action on, just removed a few lines of code to
get an error if that helps: https://sourcegraph.com/github.com/sourcegraph/cody/-/blob/vscode/src/repository/repositoryHelpers.ts?L13-19

[umpox]

FixupTest.mov

Can't replicate 🤔

Please can you double check this is the latest branch and not the previous Cody installation, @abeatrix
There's some things there that are very worrying as I have fixed all those in the past week

• Fix taking over 5s, judging from the log in your screenshot
• <selectedCode> at the start, but we just included a change in the last release that removes <selectedCode> from the start, so idk how that could happen
• The "Cody is working" message, which should be fixed as it was related to formatting issues before

[abeatrix]

So sorry @umpox, I was in the wrong branch 😭

[umpox]

@abeatrix Np, I was worried the dreaded "Cody is working" was back 😂

[abeatrix]

Yea i just tried it a couple times and I'm not seeing any leaked tags and the Cody is working forever issue 😆 Thanks for the quick fix!