typo fix in core (#2987)

substrate/core/client/src/blockchain.rs

@@ -85,7 +85,7 @@ pub trait Backend<Block: BlockT>: HeaderBackend<Block> {
 
 	/// Returns hashes of all blocks that are leaves of the block tree.
 	/// in other words, that have no children, are chain heads.
-	/// Results must be ordered best (longest, heighest) chain first.
+	/// Results must be ordered best (longest, highest) chain first.
 	fn leaves(&self) -> Result<Vec<Block::Hash>>;
 
 	/// Return hashes of all blocks that are children of the block with `parent_hash`.

substrate/core/client/src/light/backend.rs

@@ -38,7 +38,7 @@ use hash_db::Hasher;
 use trie::MemoryDB;
 use consensus::well_known_cache_keys;
 
-const IN_MEMORY_EXPECT_PROOF: &str = "InMemory state backend has Void error type and always suceeds; qed";
+const IN_MEMORY_EXPECT_PROOF: &str = "InMemory state backend has Void error type and always succeeds; qed";
 
 /// Light client backend.
 pub struct Backend<S, F, H: Hasher> {