bump runtime spec version

Author: vedhavyas

crates/subspace-runtime/src/lib.rs

@@ -128,7 +128,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
     impl_name: Cow::Borrowed("subspace"),
     authoring_version: 0,
     // The spec version can be different on Taurus and Mainnet
-    spec_version: 3,
+    spec_version: 4,
     impl_version: 0,
     apis: RUNTIME_API_VERSIONS,
     transaction_version: 0,