src: fix bug in MallocedBuffer constructor

This should be a generic type even though we are
currently only using `char` as `T`.

PR-URL: #23434
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/util.h

@@ -443,7 +443,7 @@ struct MallocedBuffer {
 
   MallocedBuffer() : data(nullptr) {}
   explicit MallocedBuffer(size_t size) : data(Malloc<T>(size)), size(size) {}
-  MallocedBuffer(char* data, size_t size) : data(data), size(size) {}
+  MallocedBuffer(T* data, size_t size) : data(data), size(size) {}
   MallocedBuffer(MallocedBuffer&& other) : data(other.data), size(other.size) {
     other.data = nullptr;
   }