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/find_path_tool.rs

@@ -31,7 +31,6 @@ pub struct FindPathToolInput {
     /// You can get back the first two paths by providing a glob of "*thing*.txt"
     /// </example>
     pub glob: String,
-
     /// Optional starting position for paginated results (0-based).
     /// When not provided, starts from the beginning.
     #[serde(default)]