[build] Update last_commit:

Revert behavior of deep= on mutable keys.

Mutable keys are a minefield for comparisons, as resolving
equality require re-implementing a lot of the internal structures, as
well as dealing with multiple mutable keys that are in the same
equivalency class by deep=.

Simplifying the implementation to not resole mutable keys is much
simpler, faster, and has the benefit that deep= and deep-not= do not
need to allocate.

last_commit.txt

@@ -1 +1 @@
-1b49934e4fd6b53e1116d5964fa639dbe28aa065
+746ced55019d07f3de25e40ce6efb20dbd4ae95b