bump version to 2.8.6 #787

Job	Run time
cargo check	1m 11s
check for no_std compatibility	1m 5s
Documentation check	1m 25s
Test Coverage	1m 25s
Minimal Versions Testing	59s
cargo hack check --feature-powerset	1m 55s
Unit, Style, and Lint Testing	3m 46s
check for semver compatibility	1m 36s
	13m 22s

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