build(flagd): pinpoint submodules to tags (#137)

Signed-off-by: Simon Schrottner <[email protected]>

Author: aepfli

.gitmodules

@@ -1,10 +1,11 @@
 [submodule "schemas"]
 	path = providers/openfeature-provider-flagd/openfeature/schemas
 	url = https://github.com/open-feature/schemas
+	branch = protobuf-v0.6.1
 [submodule "providers/openfeature-provider-flagd/test-harness"]
 	path = providers/openfeature-provider-flagd/openfeature/test-harness
 	url = [email protected]:open-feature/flagd-testbed.git
-	branch = v0.5.18
+	branch = v0.5.20
 [submodule "providers/openfeature-provider-flagd/spec"]
 	path = providers/openfeature-provider-flagd/openfeature/spec
 	url = https://github.com/open-feature/spec