Fix Typos in Comments and Documentation (#1162)

Description:  
This pull request corrects minor typographical errors in the codebase:
- In `src/pam/mod.rs`, the word "reponsible" was corrected to
"responsible" in a safety comment.
- In `src/sudoers/ast.rs`, the word "definiton" was corrected to
"definition" in the grammar documentation.

Author: maximevtush

src/pam/mod.rs

@@ -355,7 +355,7 @@ impl PamContext {
             curr_env = unsafe { curr_env.offset(1) };
         }
 
-        // SAFETY: `envs` itself was obtained by malloc(), so we are reponsible for freeing it.
+        // SAFETY: `envs` itself was obtained by malloc(), so we are responsible for freeing it.
         unsafe { libc::free(envs.cast()) };
 
         Ok(res)

src/sudoers/ast.rs

@@ -637,7 +637,7 @@ fn parse_include(stream: &mut CharStream) -> Parsed<Sudo> {
 
 /// grammar:
 /// ```text
-/// name = definition [ : name = definiton [ : ... ] ]
+/// name = definition [ : name = definition [ : ... ] ]
 /// ```
 ///
 impl<T> Parse for Def<T>