Try a slightly older snapshot date

yuvipanda · yuvipanda · commit 0a756e72dd81 · 2023-06-09T19:54:19.000+05:30
diff --git a/tests/r/r3.6-rspm/runtime.txt b/tests/r/r3.6-rspm/runtime.txt
@@ -1 +1 @@
-r-3.6-2018-12-20
+r-3.6-2018-11-31
