agent2: Clean up tool descriptions (#36619)

schemars was passing along the newlines from the doc comments. This
should make these closer to the markdown file versions we had in the old
agent.

Release Notes:

- N/A

crates/agent2/src/tools/thinking_tool.rs

@@ -11,8 +11,7 @@ use crate::{AgentTool, ToolCallEventStream};
 /// Use this tool when you need to work through complex problems, develop strategies, or outline approaches before taking action.
 #[derive(Debug, Serialize, Deserialize, JsonSchema)]
 pub struct ThinkingToolInput {
-    /// Content to think about. This should be a description of what to think about or
-    /// a problem to solve.
+    /// Content to think about. This should be a description of what to think about or a problem to solve.
     content: String,
 }