Set v6 upgrade requirements in .upgrade_requirements.json -- REVERT F…

…OR v7

This was originally created on the v7 branch, and had v7 requirements,
but we're backporting it so that people have it in-hand before v7 launches.
Since v7 hasn't launched yet, and people can use it for upgrading to new
v6's potentially, we'll make it v6 happy for now.

.upgrade_requirements.json

@@ -3,8 +3,8 @@
     "DOC2": "In other words, what you see locally are the requirements for your _current_ install",
     "DOC3": "Please don't rely on these versions for planning upgrades unless you've fetched the most recent version",
     "DOC4": "You should really just ignore it and run upgrade.php. Really",
-    "php_min_version": "8.1.0",
-    "php_max_major_minor": "8.2",
-    "php_max_wontwork": "8.3.0",
+    "php_min_version": "7.4.0",
+    "php_max_major_minor": "8.1",
+    "php_max_wontwork": "8.2.0",
     "current_snipeit_version": "6.3"
 }