Fix indexing expressions test copy/paste docs

Author: CrockAgile

src/test/incremental/hashes/indexing_expressions.rs

@@ -10,7 +10,7 @@
 
 
 // This test case tests the incremental compilation hash (ICH) implementation
-// for closure expression.
+// for indexing expression.
 
 // The general pattern followed here is: Change one thing between rev1 and rev2
 // and make sure that the hash has changed, then change nothing between rev2 and