Two small typo fixes (#6500)

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## Summary

Two small typo fixes: one in the documentation and one in a comment in
the source code I happened to come across.

crates/pep508-rs/src/marker/parse.rs

@@ -130,7 +130,7 @@ pub(crate) fn parse_marker_key_op_value<T: Pep508Url>(
     cursor.eat_whitespace();
     let r_value = parse_marker_value(cursor)?;
 
-    // Convert a `<marker_value> <marker_op> <marker_value>` expression into it's
+    // Convert a `<marker_value> <marker_op> <marker_value>` expression into its
     // typed equivalent.
     let expr = match l_value {
         // Either:

docs/guides/integration/fastapi.md

@@ -1,8 +1,8 @@
 # Using uv with FastAPI
 
-[FastAPI](https://github.com/fastapi/fastapi) is modern, high-performance Python web framework. You
-can use uv to manage your FastAPI project, including installing dependencies, managing environments,
-running FastAPI applications, and more.
+[FastAPI](https://github.com/fastapi/fastapi) is a modern, high-performance Python web framework.
+You can use uv to manage your FastAPI project, including installing dependencies, managing
+environments, running FastAPI applications, and more.
 
 !!! note