scripts/build-unit-test-docker: Update to boost 1.76.0

This is now used in openbmc/openbmc@master, so we should be using it in
the CI too.

Change-Id: I0ba9e234c1ddbb7da9694fe3eafff462604a1f83
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index e6d119d..7df74c7 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -78,7 +78,7 @@
 # Packages to include in image.
 packages = {
     "boost": PackageDef(
-        rev="1.75.0",
+        rev="1.76.0",
         url=(
             lambda pkg, rev: f"https://downloads.yoctoproject.org/mirror/sources/{pkg}_{rev.replace('.', '_')}.tar.bz2"
         ),