Remove incorrect pragma: no cover from anthropic.py line 460

The else branch at line 460-462 is actually covered by tests for
unsupported builtin tools, so the pragma: no cover is incorrect.
This was a pre-existing issue inherited from main branch.

Fixes strict-no-cover validation error.

Author: gorkachea

pydantic_ai_slim/pydantic_ai/models/anthropic.py

@@ -457,7 +457,7 @@ def _add_builtin_tools(
                     mcp_server_url_definition_param['authorization_token'] = tool.authorization_token
                 mcp_servers.append(mcp_server_url_definition_param)
                 beta_features.append('mcp-client-2025-04-04')
-            else:  # pragma: no cover
+            else:
                 raise UserError(
                     f'`{tool.__class__.__name__}` is not supported by `AnthropicModel`. If it should be, please file an issue.'
                 )