#657 prevent installation of older thecodingmachine/safe versions with ocramius/proxy-manager

Sadly, `thecodingmachine/safe` has too lax dependency ranges ( https://github.com/thecodingmachine/safe/blob/a8ab0876305a4cdaef31b2350fcb9811b5608dbc/composer.json#L106 ),
and this trips testing for lower dependency ranges in CI.

As previously highlighted multiple times on the internets, `>=` and `*` (unbounded) should be avoided
when dealing with dependency ranges, as major releases **will** break, and old dependencies will be
installed by accident.

Author: Ocramius

composer.json

@@ -27,7 +27,8 @@
     "conflict": {
         "zendframework/zend-stdlib": "<3.2.1",
         "laminas/laminas-stdlib":    "<3.2.1",
-        "doctrine/annotations":      "<1.6.1"
+        "doctrine/annotations":      "<1.6.1",
+        "thecodingmachine/safe":     "<1.3.3"
     },
     "require-dev": {
         "ext-phar":                     "*",