README: Fix `File.join` examples prefixing them by `::`
README: Fix `File.join` examples prefixing them by `::`

onddo/ssl_certificate-cookbook,onddo/ssl_certificate-cookbook,karlsvec/ssl_certificate-cookbook,zuazo/ssl_certificate-cookbook,onddo/ssl_certificate-cookbook,zuazo/ssl_certificate-cookbook,karlsvec/ssl_certificate-cookbook,karlsvec/ssl_certificate-cookbook,zuazo/ssl_certificate-cookbook