boost: 1.68.0 -> 1.69.0

The version of boost we are using should match the actual openbmc
bitbake environment if possible, openbmc/openbmc is now on 1.69.0 so we
should bump the unit test environment to match.

Change-Id: I216a9ac9e5db551eb811bcf7899262ac59dd9a10
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 105bc21..8d3b4e3 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -88,7 +88,7 @@
 # A list of package versions we are building
 # Start off by listing the stating versions of third-party sources
 declare -A PKG_REV=(
-  [boost]=1.68.0
+  [boost]=1.69.0
   [cereal]=v1.2.2
   [CLI11]=v1.7.1
   # Snapshot from 2018-12-17