fix namespace-related bugs; update dependencies

Author: mmasiukevich

.scrutinizer.yml

@@ -59,6 +59,9 @@ checks:
 build:
   nodes:
     analysis:
+      environment:
+        php:
+          version: 7.4.5
       project_setup:
         override: true
       tests:

composer.json

@@ -34,9 +34,9 @@
     "php-service-bus/common": "v4.1.*",
     "doctrine/annotations": "v1.10.*",
     "phpdocumentor/reflection-docblock": "v5.1.*",
-    "symfony/property-access": "v5.0.*",
-    "symfony/property-info":  "v5.0.*",
-    "symfony/serializer":  "v5.0.*"
+    "symfony/property-access": "v5.1.*",
+    "symfony/property-info":  "v5.1.*",
+    "symfony/serializer":  "v5.1.*"
   },
   "require-dev": {
     "php-service-bus/code-style-config": "v1.2.*",