Update av requirement from ~=15.0 to ~=16.0

[dependabot]

Updates the requirements on av to permit the latest version.

Changelog

Sourced from av's changelog.

v16.0.0

Major:

• Drop Python 3.9, Support Python 3.14.
• Drop support for i686 Linux.

Features:

• Add Filter.Context.process_command() method by :gh-user:caffeinism in (:pr:2000).
• Add packet side-data handling mechanism by :gh-user:tikuma-lsuhsc in (:pr:2003).
• Implemented set_chapters method by :gh-user:DE-AI in (:pr:2004).
• Declare free-threaded support and support 3.13t by :gh-user:ngoldbaum in (:pr:2005).
• Add writable and copyable attachment and data streams by :gh-user:skeskinen in (:pr:2026).

Fixes:

• Declare free-threaded support and support 3.13t by :gh-user:ngoldbaum in (:pr:2005).
• Allow None in FilterContext.push() type stub by :gh-user:velsinki in (:pr:2015).
• Fix typos

v15.1.0

Features:

• Support FFmpeg 8
• Make the Frame.key_frame flag writable.

v15.0.0

Major:

• Make SubtitleStream.decode() return the list of subtitles directly, making the API nicer.
• Drop support for MacOS 12 or under.
• Binary wheels: Remove libxml2 because of security concerns.
• Binary wheels: Remove xz because lzma encoding is very niche in media decoding and lesser security concerns.

Features:

• Add GBRP, GBRAP, RGBA formats by :gh-user:z-khan.
• Add VideoFrame.save(), a convenient way to save frames to PNGs or JPEGs, by :gh-user:WyattBlue.

Fixes:

• Binary wheels: Re-enable libx265, use version 4.1 by :gh-user:WyattBlue.
• Fix memory error for AudioFifo properties by :gh-user:zzjjbb.
• Copy template flags if creating a new Codec object by :gh-user:WyattBlue

... (truncated)

Commits

• 00493da Release 16.0.0
• ca69910 Writable and copyable attachment and data streams
• 61e9fc6 CI: Fix windows workflow
• d87faf7 Your bash is not my bash
• 45eaeba Prevent segfault on data stream template
• cddcef8 Use macos-15-intel runner
• c51a78d Fix VideoFrame.pts typing in tests
• 4e786dd Allow None in FilterContext.push type stub
• 8485992 Remove VideoFrame.pts stub
• 5076f8d Prevent rsync error on missing subdir
• Additional commits viewable in compare view

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