refactor(modal): remove TS1.8 support (#2644)
refactor(modal): remove TS1.8 support (#2644)


maxokorokov/core,maxokorokov/core,jnizet/ng-bootstrap,benouat/ng-bootstrap,jnizet/ng-bootstrap,fbasso/ng-bootstrap,ng-bootstrap/ng-bootstrap,jnizet/ng-bootstrap,maxokorokov/core,ktriek/ng-bootstrap,maxokorokov/core,ng-bootstrap/ng-bootstrap,jnizet/ng-bootstrap,ng-bootstrap/core,ng-bootstrap/core,ng-bootstrap/core,ktriek/ng-bootstrap,ktriek/ng-bootstrap,fbasso/ng-bootstrap,fbasso/ng-bootstrap,ng-bootstrap/ng-bootstrap,fbasso/ng-bootstrap,ng-bootstrap/ng-bootstrap,benouat/ng-bootstrap,benouat/ng-bootstrap,ktriek/ng-bootstrap,benouat/ng-bootstrap