chore: fix some minor issues in comments

Signed-off-by: houpo-bob <houpocun@outlook.com>

clippy_lints/src/infallible_try_from.rs

@@ -13,7 +13,7 @@ declare_clippy_lint! {
     ///
     /// ### Why is this bad?
     ///
-    /// Infalliable conversions should be implemented via `From` with the blanket conversion.
+    /// Infallible conversions should be implemented via `From` with the blanket conversion.
     ///
     /// ### Example
     /// ```no_run

tests/ui/manual_strip.rs

@@ -75,7 +75,7 @@ fn main() {
         s4[2..].to_string();
     }
 
-    // Don't propose to reuse the `stripped` identifier as it is overriden
+    // Don't propose to reuse the `stripped` identifier as it is overridden
     if s.starts_with("ab") {
         let stripped = &s["ab".len()..];
         //~^ ERROR: stripping a prefix manually

tests/ui/manual_unwrap_or_default.fixed

@@ -102,7 +102,7 @@ fn issue_12928() {
     let y = if let Some(Y(a, ..)) = x { a } else { 0 };
 }
 
-// For symetry with `manual_unwrap_or` test
+// For symmetry with `manual_unwrap_or` test
 fn allowed_manual_unwrap_or_zero() -> u32 {
     Some(42).unwrap_or_default()
 }

tests/ui/manual_unwrap_or_default.rs

@@ -138,7 +138,7 @@ fn issue_12928() {
     let y = if let Some(Y(a, ..)) = x { a } else { 0 };
 }
 
-// For symetry with `manual_unwrap_or` test
+// For symmetry with `manual_unwrap_or` test
 fn allowed_manual_unwrap_or_zero() -> u32 {
     if let Some(x) = Some(42) {
         //~^ manual_unwrap_or_default