Revert "fix: Work around compromised transitive dependency (#6257)" (#6262)

`mistralai` has been un-quarantined, so it should be installable again.
(We're pulling it in via `pydantic-ai`.)

This reverts commit c1921a4.

Author: sentrivana

scripts/populate_tox/config.py

@@ -310,7 +310,7 @@
         "num_versions": 2,
     },
     "pydantic_ai": {
-        "package": "pydantic-ai-slim",
+        "package": "pydantic-ai",
         "deps": {
             "*": ["pytest-asyncio"],
         },

tox.ini

@@ -477,11 +477,11 @@ deps =
     openai_agents-latest: openai-agents==0.17.0
     openai_agents: pytest-asyncio
 
-    pydantic_ai-v1.0.18: pydantic-ai-slim==1.0.18
-    pydantic_ai-v1.31.0: pydantic-ai-slim==1.31.0
-    pydantic_ai-v1.63.0: pydantic-ai-slim==1.63.0
-    pydantic_ai-v1.93.0: pydantic-ai-slim==1.93.0
-    pydantic_ai-latest: pydantic-ai-slim==1.93.0
+    pydantic_ai-v1.0.18: pydantic-ai==1.0.18
+    pydantic_ai-v1.31.0: pydantic-ai==1.31.0
+    pydantic_ai-v1.63.0: pydantic-ai==1.63.0
+    pydantic_ai-v1.93.0: pydantic-ai==1.93.0
+    pydantic_ai-latest: pydantic-ai==1.93.0
     pydantic_ai: pytest-asyncio