Bump regex from 2026.2.28 to 2026.5.9 in /tools/deps

[dependabot]

Bumps regex from 2026.2.28 to 2026.5.9.

Changelog

Sourced from regex's changelog.

Version: 2026.5.9

Reverse matching with full unicode casefolding could lead to out-of-range string indexes.

Version: 2026.4.4

A fix for older Python versions before free-threading was  supported.

Version: 2026.4.3

More fixes for free-threading.

Version: 2026.3.32

Fixed segfault.

Version: 2026.3.31

Fixed bug again.

Version: 2026.3.30

Fixed bug.

Version: 2026.3.28

Fixed version.

Version: 2026.3.27

Various fixes, including ones to improve free-threading support.

Version: 2026.2.28

Replaced atomic operations with mutex on pattern object for free-threaded Python.

Version: 2026.2.26

PR [#598](https://github.com/mrabarnett/mrab-regex/issues/598): Fix race condition in storage caching with atomic operations.
Replaced use of PyUnicode_GET_LENGTH with PyUnicode_GetLength.

Version: 2026.2.19

Added \z as alias of \Z, like in re module.
Added prefixmatch as alias of match, like in re module.

Version: 2026.1.15

... (truncated)

Commits

• e57d185 Reverse matching with full unicode casefolding lead to out-of-range string in...
• bc57b04 A fix for older Python versions before free-threading was supported.
• 773e213 More fixes for free-threading.
• 5d51c75 Fixed segfault.
• 2aff2db Fixed bug again.
• 16af8ae Fixed bug.
• 2356563 Fixed bug.
• f579e8f Fixed version.
• 55315a0 Fixed version.
• 923d78e Various fixes, including ones to improve free-threading support.
• See full diff in compare view

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.52%. Comparing base (bc1094d) to head (d29203a).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6385      +/-   ##
==========================================
- Coverage   86.53%   86.52%   -0.02%     
==========================================
  Files          98       98              
  Lines       17716    17716              
==========================================
- Hits        15331    15329       -2     
- Misses       2385     2387       +2     

Flag	Coverage Δ
functional	63.46% <100.00%> (-0.02%)	⬇️
integration	28.86% <100.00%> (ø)
unit	61.52% <100.00%> (ø)

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