chore: fix some typos in comments

Signed-off-by: forcedebug <forcedebug@outlook.com>

Author: forcedebug

bindgen-tests/tests/headers/constructors.hpp

@@ -1,6 +1,6 @@
 
 class TestOverload {
-  // This one shouldnt' be generated.
+  // This one shouldn't be generated.
   TestOverload();
 public:
   TestOverload(int);

bindgen-tests/tests/headers/constructors_1_33.hpp

@@ -1,7 +1,7 @@
 // bindgen-flags: --rust-target 1.33
 
 class TestOverload {
-  // This one shouldnt' be generated.
+  // This one shouldn't be generated.
   TestOverload();
 public:
   /// Calling this should use `mem::unintialized()` and not `MaybeUninit()` as only rust 1.36 includes that.

bindgen/ir/comp.rs

@@ -1449,7 +1449,7 @@ impl CompInfo {
                 }
                 CXCursor_TemplateTypeParameter => {
                     let param = Item::type_param(None, cur, ctx).expect(
-                        "Item::type_param should't fail when pointing \
+                        "Item::type_param shouldn't fail when pointing \
                          at a TemplateTypeParameter",
                     );
                     ci.template_params.push(param);