Add source to voice search pixel schema (#7134)

Task/Issue URL:
https://app.asana.com/1/137249556945/project/488551667048375/task/1211967741651879?focus=true

### Description

- Adds “source" to voice search pixel schema

### Steps to test this PR

- [ ] Code review

Author: joshliebe

PixelDefinitions/params_dictionary.json

@@ -66,5 +66,11 @@
         "type": "string",
         "description": "Final status of the wide event flow",
         "enum": ["SUCCESS", "FAILURE", "CANCELLED", "UNKNOWN"]
+    },
+    "source": {
+        "key": "source",
+        "type": "string",
+        "description": "Source from which voice search was launched",
+        "enum": ["browser", "widget"]
     }
 }

PixelDefinitions/pixels/voice_search.json5

@@ -4,20 +4,20 @@
         "owners": ["joshliebe"],
         "triggers": ["other"],
         "suffixes": ["form_factor"],
-        "parameters": ["appVersion"]
+        "parameters": ["appVersion", "source"]
     },
     "m_voice_search_aichat_done": {
         "description": "User completed a voice search with the Duck.ai mode selected.",
         "owners": ["joshliebe"],
         "triggers": ["other"],
         "suffixes": ["form_factor"],
-        "parameters": ["appVersion"]
+        "parameters": ["appVersion", "source"]
     },
     "m_voice_search_cancelled": {
         "description": "User canceled a voice search.",
         "owners": ["joshliebe"],
         "triggers": ["other"],
         "suffixes": ["form_factor"],
-        "parameters": ["appVersion"]
+        "parameters": ["appVersion", "source"]
     }
 }