chore(deps): update dependency providers/openfeature-provider-flagd/openfeature/test-harness to v2 (open-feature#178)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.gitmodules

@@ -5,7 +5,7 @@
 [submodule "providers/openfeature-provider-flagd/test-harness"]
 	path = providers/openfeature-provider-flagd/openfeature/test-harness
 	url = [email protected]:open-feature/flagd-testbed.git
-	branch = v0.5.21
+	branch = v2.1.0
 [submodule "providers/openfeature-provider-flagd/spec"]
 	path = providers/openfeature-provider-flagd/openfeature/spec
 	url = https://github.com/open-feature/spec