Update dependency elixir to v1.20.4

[renovate]

This PR contains the following updates:

Package	Update	Change
elixir (source)	patch	1.20.3 → 1.20.4

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Release Notes

elixir-lang/elixir (elixir)

v1.20.4

Compare Source

1. Security

• [List] Avoid recursion when invalid charlists are given to List.to_string/1 or List.to_charlist/1 (CVE-2026-75758, GHSA-jf5q-v438-665c)

2. Bug fixes

Elixir

• [Base] Fix false positives in Base64 validation
• [Kernel] Fix inferred type of :erlang.split_binary/2 when given a bitstring
• [Kernel] Fix type checker crash on comprehensions with a non-returning :into expression
• [String] Fix final sigma handling in Greek casing
• [Task] Fix Task.yield_many/2 waiting indefinitely when :limit exceeds the task count

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