Fix #86c89ftg9 - Remove PHP 7.4 typed properties for PHP 7.3 compatibility

Remove typed property declarations to prevent fatal parse errors on
Moodle 4.0.x servers running PHP 7.3. Lower environment.xml PHP
requirement from 7.4 to 7.3.

Fixes #13

classes/condition.php

@@ -42,14 +42,14 @@ class condition extends \core_availability\condition {
      *
      * @var string
      */
-    protected string $ipaddresses = '';
+    protected $ipaddresses = '';
 
     /**
      * Predefined IP address ranges.
      *
      * @var array
      */
-    protected array $predefinedranges = [];
+    protected $predefinedranges = [];
 
     /**
      * condition constructor.

environment.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <COMPATIBILITY_MATRIX>
     <PLUGIN name="availability_ipaddress">
-        <PHP version="7.4" level="required"/>
+        <PHP version="7.3" level="required"/>
     </PLUGIN>
 </COMPATIBILITY_MATRIX>