[HIPIFY][perl] Add "important" notice

# IMPORTANT: Do not change this file manually: it is generated by hipify-clang --perl


[ROCm/hip commit: 876af8f381]

projects/hip/bin/hipify-perl

@@ -22,6 +22,8 @@
 # THE SOFTWARE.
 ##
 
+# IMPORTANT: Do not change this file manually: it is generated by hipify-clang --perl
+
 #usage hipify-perl [OPTIONS] INPUT_FILE
 
 use Getopt::Long;