MDL-76415 core: Fixed ${var} string interpolation deprecations.

Since PHP 8.2, placing the dollar sign outside the curly brace is deprecated when
the expression inside the braces resolves to a variable or an expression.

lib/phpminimumversionlib.php

@@ -53,7 +53,7 @@ function moodle_minimum_php_version_is_met($haltexecution = false) {
 
     if (version_compare(PHP_VERSION, $minimumversion) < 0) {
         if ($haltexecution) {
-            $error = "Moodle ${moodlerequirementchanged} or later requires at least PHP ${minimumversion} "
+            $error = "Moodle {$moodlerequirementchanged} or later requires at least PHP {$minimumversion} "
                 . "(currently using version " . PHP_VERSION .").\n"
                 . "Some servers may have multiple PHP versions installed, are you using the correct executable?\n";