Remove IncRefError, DecRefError and StoredMapError (#9384)

All of them are a subset of `DispatchError` anyway, no need to have
special errors IMHO.

substrate/primitives/runtime/src/traits.rs

@@ -152,25 +152,6 @@ impl From<BadOrigin> for &'static str {
 	}
 }
 
-/// Error that can be returned by our impl of `StoredMap`.
-#[derive(Encode, Decode, RuntimeDebug)]
-pub enum StoredMapError {
-	/// Attempt to create map value when it is a consumer and there are no providers in place.
-	NoProviders,
-	/// Attempt to anull/remove value when it is the last provider and there is still at
-	/// least one consumer left.
-	ConsumerRemaining,
-}
-
-impl From<StoredMapError> for &'static str {
-	fn from(e: StoredMapError) -> &'static str {
-		match e {
-			StoredMapError::NoProviders => "No providers",
-			StoredMapError::ConsumerRemaining => "Consumer remaining",
-		}
-	}
-}
-
 /// An error that indicates that a lookup failed.
 #[derive(Encode, Decode, RuntimeDebug)]
 pub struct LookupError;