Update dependency abseil-cpp to v20260817

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
abseil-cpp	bazel_dep	major	20260526.0 → 20260817.0

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Release Notes

abseil/abseil-cpp (abseil-cpp)

v20260817.0: Abseil LTS branch, August 2026

Compare Source

Abseil LTS 2026081.0

What's New

• Added URL escaping utilities
• Many bug fixes and optimizations

Breaking Changes

• absl::void_t is now deprecated; users should use C++17 std::void_t directly.
• Hashtable iterators returned from insert/emplace are now non-iterable (any prior use of iteration was likely a bug).

Known Issues

• None at this time

Baseline: 2065f4d

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