[llvm][NFC]Fix a few typos (#110844)

Author: spacey-sooty

llvm/include/llvm/Support/ConvertUTF.h

@@ -47,7 +47,7 @@
 
     Conversions between UTF32, UTF-16, and UTF-8.  Header file.
 
-    Several funtions are included here, forming a complete set of
+    Several functions are included here, forming a complete set of
     conversions between the three formats.  UTF-7 is not included
     here, but is handled in a separate source file.
 

llvm/include/llvm/Support/MathExtras.h

@@ -723,7 +723,7 @@ std::enable_if_t<std::is_signed_v<T>, T> AddOverflow(T X, T Y, T &Result) {
 }
 
 /// Subtract two signed integers, computing the two's complement truncated
-/// result, returning true if an overflow ocurred.
+/// result, returning true if an overflow occurred.
 template <typename T>
 std::enable_if_t<std::is_signed_v<T>, T> SubOverflow(T X, T Y, T &Result) {
 #if __has_builtin(__builtin_sub_overflow)
@@ -749,7 +749,7 @@ std::enable_if_t<std::is_signed_v<T>, T> SubOverflow(T X, T Y, T &Result) {
 }
 
 /// Multiply two signed integers, computing the two's complement truncated
-/// result, returning true if an overflow ocurred.
+/// result, returning true if an overflow occurred.
 template <typename T>
 std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
 #if __has_builtin(__builtin_mul_overflow)