[cleanup] remove legacy path condition in jest preprocessor

[ldirer]

Summary

This PR removes a condition that looks legacy inside Jest preprocessor script.

How I happened upon this:

Running yarn test on a fresh clone of the repository, I ran into Jest errors suggesting files were not transformed properly by babel.

I tracked it down to a condition in scripts/jest/preprocessor.js:

if (!filePath.match(/\/third_party\//)) {
    ...
}

I had cloned the repo on my machine inside a third_party/react directory, causing this condition to always be false 🥲 .

How did you test this change?

Research done:

• I only found one third_party directory, and it was inside node_modules (hence already ignored by babel transforms).
• I looked at the git history with git log --diff-filter=ACDR -- '*third_party*'.
• This confirmed the third_party folder existed at some point in the codebase and was removed in commit 8b4ec79.

Running yarn test before/after the change produces the same output in the general case.
If running yarn test with a path like third_party/react, the command fails before this change and passes after.

This seemed like a tiny fix so I did not open an issue.

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Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 26, 2024 1:25am

[ldirer]

This really should be a minor change, I think the diff is a bit misleading.
This would be a "minus 3 lines" diff if the condition on main had been inverted to look as follows:

if (filePath.match(/\/third_party\//)) {
    return {code: src}
}

Anyway, here's a Dockerfile that reproduces the issue when placed at the root of the repository.
It runs tests twice as part of the build: the first set of tests passes, the second does not (due to the name of the containing folder).

Expected reproduction before this PR: docker build -t react-tests ./ fails on the second RUN yarn test command.

FROM node:18.20.1

WORKDIR /app

COPY . .

RUN yarn install

# Run tests - these should pass
RUN yarn test

RUN mv /app /third_party

WORKDIR /third_party
# these will fail
RUN yarn test