Don't install mongo legacy driver on PHP 8

Author: BanzaiMan

bin/compile-extension-mongo

@@ -5,7 +5,7 @@ source $(dirname $0)/compile-extensions-common
 
 travis_time_start
 
-if [[ ! $VERSION =~ ^7 && ! $VERSION =~ ^master$ ]]; then
+if [[ ! $VERSION =~ ^7 ! $VERSION =~ ^8 && ! $VERSION =~ ^master$ ]]; then
 	git clone https://github.com/mongodb/mongo-php-driver-legacy.git
 	pushd mongo-php-driver-legacy
 	git checkout 1.6.16