chore: Increase minimum version of tecnickcom/tcpdf

Author: mitelg

composer.json

@@ -39,7 +39,7 @@
     "require-dev": {
         "phpunit/phpunit": "^7",
         "setasign/fpdf": "~1.8.6",
-        "tecnickcom/tcpdf": "^6.2",
+        "tecnickcom/tcpdf": "^6.8",
         "setasign/tfpdf": "~1.33",
         "squizlabs/php_codesniffer": "^3.5"
     },