adjust indentation

lectures/22_hash_tables_I/README.md

@@ -160,8 +160,9 @@ satisfy the second.
 ```cpp
 unsigned int hash(string const& k, unsigned int N) {
 	unsigned int value = 0;
-for (unsigned int i=0; i<k.size(); ++i)
+	for (unsigned int i=0; i<k.size(); ++i) {
 		value += k[i]; // conversion to int is automatic
+	}
 	return value % N;
 }
 ```