Update dependency com.squareup.okio:okio to v3.15.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
com.squareup.okio:okio	3.10.2 -> 3.15.0

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Release Notes

square/okio (com.squareup.okio:okio)

v3.15.0

2025-07-01

• Upgrade: [kotlinx-datetime 0.7.0-0.6.x-compat][datetime_0_7_0_compat]. The previous 3.14.0
  release, FakeFileSystem broke binary-compatibility for calls to FakeFileSystem(). This
  restores that compatibility.

• Breaking: Change FakeFileSystem.clock from a JVM field to a property. This avoids a crash
  running Okio in a Gradle 8.x plugin. This change is not binary-compatible.

v3.14.0

2025-06-28

• Upgrade: [kotlinx-datetime 0.7.0][datetime_0_7_0]. This impacts the okio-fakefilesystem
  artifact only. This is a binary-incompatible backwards-incompatible change that cannot co-exist
  with previous releases of okio-fakefilesystem! If you observe a NoSuchMethodError calling
  FakeFileSystem.init, update the calling code to this release (or newer) and recompile. We don't
  like imposing backwards-incompatible changes like this on you and do so regretfully.

v3.13.0

2025-06-13

• New: okio.Socket interface. This is a first step towards low-level streaming networking support
  for Kotlin/Multiplatform. This release provides two JVM-only implementations: asOkioSocket()
  adapts a java.net.Socket to our new interface, and inMemorySocketPair() returns a pair of
  mutually-connected sockets. We also anticipate that this interface will be a useful abstraction
  for proxies and tunnels.
• New: In-development snapshots are now published to the [Central Portal Snapshots repository].

v3.12.0

2025-05-27

• New: Support an optional end index when searching with BufferedSource.indexOf().
• Fix: Don't do unnecessary work in BufferedSource.rangeEquals().
• Upgrade: [Kotlin 2.1.21][kotlin_2_1_21].

v3.11.0

2025-04-09

• Fix: Clear the deflater's byte array reference
• New: Faster implementation of String.decodeHex() on Kotlin/JS.
• New: Declare EXACTLY_ONCE execution for blocks like Closeable.use {} and FileSystem.read {}.
• Upgrade: [Kotlin 2.1.20][kotlin_2_1_20].

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