Revert "[master] Bump mono to head of 2019-06"

This reverts commit edadae301e.
2019-08-12 16:50:23 -04:00 · 2019-08-12 16:50:23 -04:00 · ed8252f12d
--- a/mk/mono.mk
+++ b/mk/mono.mk
@ -1,4 +1,4 @@
-NEEDED_MONO_VERSION := 4365dce8b7dfdb42837bfd11bb61284b3477a45e
+NEEDED_MONO_VERSION := 17ac7dcfc74e7371b99a1b7bf73d17e78df90c55
 NEEDED_MONO_BRANCH := 2019-06

 MONO_DIRECTORY := mono