tr2/objects/bird_guardian: remove hard-coded end level behaviour

This removes the hard-coded end level behaviour of the bird guardian in
TR2. For OG, an injection is provided to add a command to the death
animation to yield the same result; custom levels can modify the object
accordingly externally.

Resolves #1583.

data/tr2/ship/cfg/TR2X_gameflow.json5

@@ -309,6 +309,7 @@
             ],
             "injections": [
                 "data/injections/common_pickup_meshes.bin",
+                "data/injections/guardian_death_commands.bin",
                 "data/injections/palace_fd.bin",
                 "data/injections/palace_itemrots.bin",
             ],

data/tr2/ship/cfg/TR2X_gameflow_gm.json5

@@ -106,6 +106,9 @@
                 {"type": "total_stats", "background_path": "data/images/end.png"},
                 {"type": "level_complete"},
             ],
+            "injections": [
+                "data/injections/guardian_death_commands.bin",
+            ],
         },
 
         // 5. Nightmare in Vegas
@@ -124,6 +127,9 @@
                 {"type": "level_stats"},
                 {"type": "level_complete"},
             ],
+            "injections": [
+                "data/injections/guardian_death_commands.bin",
+            ],
         },
     ],