fix(deps): update dependency rxjs to v7

package.json

@@ -68,7 +68,7 @@
     "ng-katex": "2.0.3",
     "ng2-pdf-viewer": "^7.0.1",
     "parse-color": "1.0.0",
-    "rxjs": "6.6.7",
+    "rxjs": "7.8.1",
     "subsink": "1.0.2",
     "tslib": "2.3.1",
     "winston": "^3.8.2",

yarn.lock

@@ -10742,6 +10742,13 @@ [email protected], rxjs@^6.6.2:
   dependencies:
     tslib "^1.9.0"
 
+[email protected]:
+  version "7.8.1"
+  resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-7.8.1.tgz#6f6f3d99ea8044291efd92e7c7fcf562c4057543"
+  integrity sha512-AA3TVj+0A2iuIoQkWEK/tqFjBq2j+6PO6Y0zJcvzLAFhEFIO3HL0vls9hWLncZbAAbK0mar7oZ4V079I/qPMxg==
+  dependencies:
+    tslib "^2.1.0"
+
 rxjs@^5.5.6:
   version "5.5.12"
   resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-5.5.12.tgz#6fa61b8a77c3d793dbaf270bee2f43f652d741cc"