Release 3.1.0 (#500)

* Update CHANGELOG

* Remove version 3.1.0 details from CHANGELOG

Removed duplicate details for version 3.1.0 from CHANGELOG.md.

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Co-authored-by: dd-octo-sts[bot] <200755185+dd-octo-sts[bot]@users.noreply.github.com>
Co-authored-by: Nathan Tournant <nathan.tournant@datadoghq.com>

Author: dd-octo-sts[bot]

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixed
 * Support Synthetics Test Suites by @melkouri in https://github.com/DataDog/datadog-sync-cli/pull/478
 * Fix Rum sessions in synthetics browser tests by @melkouri in https://github.com/DataDog/datadog-sync-cli/pull/483
+* fix: handle GCS stale generation and NotFound during state loading by @michael-richey in https://github.com/DataDog/datadog-sync-cli/pull/499
 ### Added
 * NDJSON stack 1/4: ResourceOutcome model, shared writer, --json flag, and outcome emission by @nathantournant in https://github.com/DataDog/datadog-sync-cli/pull/484
 * NDJSON stack 2/4: Log class NDJSON mode by @nathantournant in https://github.com/DataDog/datadog-sync-cli/pull/489