Fix some typos

src/compiler-debugging.md

@@ -324,7 +324,7 @@ reveal the actual MIR elements, as text.
 
 To view these files, simply use a modern browser, or a CSS-capable HTML preview
 feature in a modern IDE. (The default HTML preview pane in *VS Code* is known to
-work, for instance.
+work, for instance.)
 
 ## Narrowing (Bisecting) Regressions
 

src/tests/intro.md

@@ -70,7 +70,7 @@ including:
   is correct. The formatting check is also automatically run by the Tidy tool
   mentioned above.
 
-  Example: `./x.py fmt --check` checks formatting an exits with an error if
+  Example: `./x.py fmt --check` checks formatting and exits with an error if
   formatting is needed.
 
   Example: `./x.py fmt` runs rustfmt on the codebase.