[NFC][SYCL][ESIMD] Delete copy and move assignment operators. (#17682)

Delete copy and move assignment operators to comply with Rule of Five.

Author: maarquitos14

llvm/lib/SYCLLowerIR/ESIMD/ESIMDVerifier.cpp

@@ -97,6 +97,8 @@ class BuffDeleter {
   BuffDeleter() = delete;
   BuffDeleter(const BuffDeleter &) = delete;
   BuffDeleter(BuffDeleter &&) = delete;
+  BuffDeleter &operator=(BuffDeleter &) = delete;
+  BuffDeleter &operator=(BuffDeleter &&) = delete;
 
 private:
   char *Buff;