perf: remove unnecessary regex s modifier

[MajedMuhammad]

Description

Minor bug fix:

Fixes bug caused by this commit: 2687dbb
It is just a regex equivalent replacement:
. with s modifier is 100% equal to [\s\S] without s modifier.

s modifier is causing older browsers to fail with a blank page with console error such as:
SyntaxError: invalid regular expression flag s

Future Consideration

Please avoid accepting PRs that include commits including regex s modifier/flag.

---

What is the purpose of this pull request?

• Bug fix X
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines, especially the Pull Request Guidelines. X
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate. X
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123). X
• Update the corresponding documentation if needed. X
• Ideally, include relevant tests that fail without this PR but pass with it.

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[MajedMuhammad]

@patak-dev, sorry for mentioning you for a very minor bug.
However, you may want to accept this PR, it is nothing, but it just keeps support for legacy browsers.
No impact at all, it is equivalent.

[bluwy]

The browsers supported by Vite should also support the s modifier, so I don't think we should avoid using this because of that.

But now that you brought this up, it doesn't look like we need to use the s modifier in the first place. The strings we're dealing with should always only be a single line. I think we can simply remove the s modifier as a perf improvement, and we can do the same for the others: https://github.com/search?q=repo%3Avitejs%2Fvite%20%2F%5B%3F%23%5D.*%24%2Fs&type=code

[MajedMuhammad]

@bluwy, done. You may want to merge.

[bluwy]

Thanks!