fix deepseek deseret regex

[dhiltgen]

On windows compiled with gcc the c++ regex library failed to handle the characters

Resolves the problem first reported here - #7118 (comment)

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[slaren]

Please check the CI result, 4 - test-tokenizer-0-deepseek-llm (Failed) is failing.

[dhiltgen]

Bummer. It looks like this approach only works with clang.