refactor: removed unused type

Author: Bikappa

docs/UPGRADING.md

@@ -4,6 +4,9 @@ Here you can find a list of migration guides to handle breaking changes between
 
 ## 0.32.0
 
+In the gRPC API the type `PlatformLoadingError` is dropped. Now a `FailedInstanceInitError` is returned as error details
+instead of it with the reason field set to `FAILED_INSTANCE_INIT_REASON_PLATFORM_LOAD_ERROR`.
+
 Configuration file lookup in current working directory and its parents is dropped. The command line flag `--config-file`
 must be specified to use an alternative configuration file from the one in the data directory.