Bump version for 5.8.6

[eliasyishak]

For fix upstream bug:

• Version solving failed for intl: 0.19.0 with flutter_localizations flutter/flutter#139861

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[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:unified_analytics	5.8.6	ready to publish	unified_analytics-v5.8.6
package:cli_config	0.2.0	already published at pub.dev
package:extension_discovery	2.0.1-wip	WIP (no publish necessary)
package:graphs	2.3.2-wip	WIP (no publish necessary)

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[christopherfujino]

LGTM