Roll src/third_party/boringssl/src 78b3337a1..2309f645e

https://boringssl.googlesource.com/boringssl/+log/78b3337a10a7f7b3495b6cb8140a74e265290898..2309f645e509507a1cc8f9845771110fcf986fd9

The following commits have update notes:
  9701e84ef Remove RAND_set_urandom_fd.

Bug: none
Change-Id: I491b0f82ef9381e445cc38f19cc8520874b7a6f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2220279
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Steven Valdez <svaldez@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773801}

DEPS

@@ -205,7 +205,7 @@ vars = {
   #
   # Note this revision should be updated with
   # third_party/boringssl/roll_boringssl.py, not roll-dep.
-  'boringssl_revision': '78b3337a10a7f7b3495b6cb8140a74e265290898',
+  'boringssl_revision': '2309f645e509507a1cc8f9845771110fcf986fd9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling google-toolbox-for-mac
   # and whatever else without interference from each other.