Bump version to 2.6.5

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Bump version to 2.6.1 (mastodon#9172)

Bump version to 2.6.0 (mastodon#9149)

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Bump version to 2.6.0rc4 (mastodon#9164)

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Bump version to 2.6.0rc3 (mastodon#9142)

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Bump version to 2.6.0rc2 (mastodon#9087)

* Bump version to 2.6.0rc2

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Bump version to 2.6.0rc1 (mastodon#9025)

* Bump version to 2.6.0rc1

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