MDL-71747 composer: Regenerate with php74 and requirements raised

Now that the required PHP version has been raised to php74, set
it in the composer.json file and regenerate everything, following
the instructions @ https://docs.moodle.org/dev/Composer, also
with php74.

That's the only change (raised php version) as far as no change
has been performed to extension.

composer.json

@@ -28,7 +28,7 @@
     "minimum-stability": "dev",
     "prefer-stable": true,
     "require": {
-        "php": ">=7.3.0",
+        "php": ">=7.4.0",
         "ext-iconv": "*",
         "ext-mbstring": "*",
         "ext-curl": "*",