Don't remove forward slashes in regex

[svile]

When passing a regex without any flags to string().pattern(regex) all forward slashes within the regex would be removed. This fix removes only forward slashes (with flags if any) from the end of the regex string.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[climba03003]

LGTM. @aboutlo Can you take a look on it?

[mcollina]

lgtm

[coveralls]

Pull Request Test Coverage Report for Build 788929602

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.554%

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Totals
Change from base Build 788612384:	0.0%
Covered Lines:	408
Relevant Lines:	408

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 788929602

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.554%

---

Totals
Change from base Build 788612384:	0.0%
Covered Lines:	408
Relevant Lines:	408

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💛 - Coveralls