Remove agent dependency from Perplexity bridge

SearchResultProcessor was removed in main branch, so the agent
dependency is no longer needed.

Author: OskarStark

src/platform/src/Bridge/Perplexity/composer.json

@@ -26,7 +26,6 @@
     ],
     "require": {
         "php": ">=8.2",
-        "symfony/ai-agent": "@dev",
         "symfony/ai-platform": "@dev",
         "symfony/http-client": "^7.3|^8.0"
     },