docs: backtick parameter references in API comments

std/hashmap/hashmap.hon

@@ -29,7 +29,7 @@ StringHashMap proc($V type) type {
     return HashMap([]u8, V, str_hash, str_eql)
 }
 
-#! retain allocator for later growth and cleanup; this call does not allocate.
+#! retain `allocator` for later growth and cleanup; this call does not allocate.
 init proc(
     $K, $V type,
     $hash_key proc(key K) usize,