update angular core to version 8

package.json

@@ -25,7 +25,7 @@
   "devDependencies": {
     "@angular-devkit/schematics": "^9.0.1",
     "@angular/animations": "^8.2.14",
-    "@angular/cdk": "^7.3.7",
+    "@angular/cdk": "^8.2.3",
     "@angular/cdk-experimental": "^7.3.7",
     "@angular/common": "^8.2.14",
     "@angular/compiler": "^8.2.14",
@@ -35,7 +35,7 @@
     "@angular/forms": "^8.2.14",
     "@angular/http": "^7.2.15",
     "@angular/language-service": "^8.2.14",
-    "@angular/material": "^7.3.7",
+    "@angular/material": "^8.2.3",
     "@angular/platform-browser": "^8.2.14",
     "@angular/platform-browser-dynamic": "^8.2.14",
     "@angular/router": "^8.2.14",