Fix re2c requirement info

Cf. <php/php-src#6593>.

Author: cmb69

install/unix/index.xml

@@ -76,7 +76,7 @@
      </listitem>
      <listitem>
       <simpara>
-       re2c: 0.13.4+ (for PHP &gt; 7.0.0), 0.13.7+ (for PHP &gt; 8.0.0)
+       re2c: 0.13.4+
       </simpara>
      </listitem>
      <listitem>