Only run GC 3 times instead of 4 to scrub (#350)

* Only run GC 3 times instead of 4 to scrub

Per slack, 'Diogo changed it so it only needs 3 to promote everything to old generation now'.

* Still run gc 4 times on older Julia versions

* Format

Author: Zentrik

src/execution.jl

@@ -1,7 +1,14 @@
 # Trigger several successive GC sweeps. This is more comprehensive than running just a
 # single sweep, since freeable objects may need more than one sweep to be appropriately
 # marked and freed.
-gcscrub() = (GC.gc(); GC.gc(); GC.gc(); GC.gc())
+function gcscrub()
+    GC.gc()
+    GC.gc()
+    GC.gc()
+    @static if VERSION < v"1.10"
+        GC.gc()
+    end
+end
 
 #############
 # Benchmark #