Fixed some grammar errors (#1599)

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Divanshu Chauhan <23524935+Divkix@users.noreply.github.com>

common/ostream.h

@@ -78,9 +78,9 @@ namespace llvm {
 // this, and so we want to prioritize accordingly.
 //
 // It would be slightly cleaner for LLVM itself to provide this overload in
-// `raw_os_ostream.h` so that we wouldn't need to inject into its namespace, but
-// supporting `std::ostream` isn't a priority for LLVM so we handle it locally
-// instead.
+// `raw_os_ostream.h` so that we wouldn't need to inject into LLVM's namespace,
+// but supporting `std::ostream` isn't a priority for LLVM so we handle it
+// locally instead.
 template <typename S, typename T,
           typename = std::enable_if_t<std::is_base_of_v<
               std::ostream, std::remove_reference_t<std::remove_cv_t<S>>>>,

toolchain/parser/parse_node_kind.h

@@ -41,8 +41,9 @@ class ParseNodeKind {
   }
 #include "toolchain/parser/parse_node_kind.def"
 
-  // The default constructor is deleted as objects of this type should always be
-  // constructed using the above factory functions for each unique kind.
+  // The default constructor is deleted because objects of this type should
+  // always be constructed using the above factory functions for each unique
+  // kind.
   ParseNodeKind() = delete;
 
   friend auto operator==(ParseNodeKind lhs, ParseNodeKind rhs) -> bool {
@@ -57,7 +58,7 @@ class ParseNodeKind {
 
   // Enable conversion to our private enum, including in a `constexpr` context,
   // to enable usage in `switch` and `case`. The enum remains private and
-  // nothing else should be using this.
+  // nothing else should be using this function.
   // NOLINTNEXTLINE(google-explicit-constructor)
   constexpr operator KindEnum() const { return kind_; }