#!/bin/sh wc <<< "$1"
#!/bin/sh wc << EOF $1 EOF
Your script uses a shell feature not supported by the shebang. Either rewrite the script to be portable, or change the shebang to explicitly require a shell like Bash. In this specific case, the here-string can be replaced by a single-line here document as shown.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.