build-unit-test-docker: Dependency updates

fmt: 6.1.2 -> 6.2.1
catch2: 2.11.1 -> 2.12.2

Change-Id: I06d23312333f00a84104a9a6151cda58908f244d
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 5d02405..6b658a3 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -97,9 +97,9 @@
 declare -A PKG_REV=(
   [boost]=1.73.0
   [cereal]=v1.2.2
-  [catch2]=v2.11.1
+  [catch2]=v2.12.2
   [CLI11]=v1.9.0
-  [fmt]=6.1.2
+  [fmt]=6.2.1
   # Snapshot from 2020-01-03
   [function2]=3a0746bf5f601dfed05330aefcb6854354fce07d
   # Snapshot from 2020-02-13