fix: add Float32 to LCNF.builtinRuntimeTypes list (#6837)

This PR adds Float32 to the LCNF builtinRuntimeTypes list. This was
missed during the initial Float32 implementation, but this omission has
the side effect of lowering Float32 to obj in the IR.

src/Lean/Compiler/LCNF/Util.lean

@@ -80,7 +80,7 @@ List of types that have builtin runtime support
 def builtinRuntimeTypes : List Name := [
   ``String,
   ``UInt8, ``UInt16, ``UInt32, ``UInt64, ``USize,
-  ``Float,
+  ``Float, ``Float32,
   ``Thunk, ``Task,
   ``Array, ``ByteArray, ``FloatArray,
   ``Nat, ``Int