v20.9.0

Another small but important release, mostly oriented towards fixing a couple of bugs with the new UPS APIs.
Remember, the old UPS XML APIs will be shut down on 3rd June 2024.

What's Changed

• Fixed unable to select "free method" in UPS backend configuration by @fballiano in #4005
• Fixed erroneous call to getText() method in Mage_Usa_Model_Shipping_Carrier_Ups::getAllowedMethods() by @ragnese in #4013
• Fixed available currencies filtering in UPS _parseRestResponse() method by @fballiano in #4017
• Added "edit" action column to "Associated Products" grid of grouped products by @empiricompany in #4006
• Fixed customer can't login after registering through PayPal Express Checkout by @fballiano in #3979
• Added filemtime to merged JS/CSS hash calculation algorithm by @boesbo in #4004
• Added stopPropagation to "copy text" buttons in backend by @Caprico85 in #4019
• Updated PHPStan to 1.11.2 by @fballiano in #3988
• Bump squizlabs/php_codesniffer from 3.9.2 to 3.10.1 by @dependabot in #4011
• Bump friendsofphp/php-cs-fixer from 3.57.1 to 3.57.2 by @dependabot in #4012