Deprecated function: Creation of dynamic property

Tested with version 3.8 of the AMP module in PHP 8.3.
The Merge Request resolves the deprecated issue and does not result in a new issue.

I update the issue in RTBC.

Thanks for your fix !

Also confirmed that the supplied MR resolved the issue for my site using PHP 8.2 and the dev version of the module. Thank you!

After this patch, I got the following notices in my console after for example a drush updb command:

PHP Deprecated:  Using ${var} in strings is deprecated, use {$var} instead in /var/www/html/vendor/lullabot/amp/src/AMP.php on line 356

Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /var/www/html/vendor/lullabot/amp/src/AMP.php on line 356
PHP Deprecated:  Using ${var} in strings is deprecated, use {$var} instead in /var/www/html/vendor/lullabot/amp/src/AMP.php on line 357

Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /var/www/html/vendor/lullabot/amp/src/AMP.php on line 357

I fixed this by adding this patch in my projects composer.json file:

			"lullabot/amp": {
				"#317": "https://patch-diff.githubusercontent.com/raw/Lullabot/amp-library/pull/317.patch"
			}

I also confirm the patch fixes the issue as described. Also comment #6 makes sense as well. Thank you all!