build-unit-test-docker: Update valijson to v0.4

v0.4 contains 66262bafb82c ("Include nlohmann/json.hpp instead of
json.hpp") which resolves some subproject build issues with
entity-manager.

Change-Id: Ic1817abe0ac022b4cb1afed67aa6ac8a649519d0
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 8230ee0..a6ef62c 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -181,10 +181,10 @@
             "-DBOOST_URL_STANDALONE=ON",
         ],
     ),
-    # version from ./meta-openembedded/meta-oe/dynamic-layers/networking-layer/recipes-devtools/valijson/valijson_0.3.bb
-    # Snapshot from 2020-12-02 - fix for curlpp dependency
+    # valijson v0.4, which contains the nlohmann/json.hpp include fix:
+    # 66262bafb82c ("Include nlohmann/json.hpp instead of json.hpp")
     "tristanpenman/valijson": PackageDef(
-        rev="8cc83c8be9c1c927f5da952b2333b30e5f0353be",
+        rev="v0.4",
         build_type="cmake",
         config_flags=[
             "-Dvalijson_BUILD_TESTS=0",