remove "font-display" declaration to avoid flickering

lib/single-file/modules/css-fonts-minifier.js

@@ -117,8 +117,17 @@ this.fontsMinifier = this.fontsMinifier || (() => {
 						removedRules.push(cssRule);
 					}
 				}
+				const removedDeclarations = [];
+				for (let declaration = ruleData.block.children.head; declaration; declaration = declaration.next) {
+					if (declaration.data.property == "font-display") {
+						removedDeclarations.push(declaration);
 					}
 				}
+				if (removedDeclarations.length) {
+					removedDeclarations.forEach(removedDeclaration => ruleData.block.children.remove(removedDeclaration));
+				}
+			}
+		}
 		removedRules.forEach(cssRule => cssRules.remove(cssRule));
 	}