chore: Upgrade RxJS dev dep to v7.

package.json

@@ -30,7 +30,7 @@
     "mocha": "^8.0.0",
     "prettier": "^2.0.0",
     "rimraf": "^3.0.0",
-    "rxjs": "^6.0.0",
+    "rxjs": "^7.0.0",
     "ts-node": "^9.0.0",
     "typescript": "~4.2.2"
   },

yarn.lock

@@ -2077,13 +2077,20 @@ rxjs-report-usage@^1.0.4:
     glob "~7.1.6"
     prompts "~2.3.2"
 
-rxjs@^6.0.0, rxjs@^6.6.7:
+rxjs@^6.6.7:
   version "6.6.7"
   resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-6.6.7.tgz#90ac018acabf491bf65044235d5863c4dab804c9"
   integrity sha512-hTdwr+7yYNIT5n4AMYp85KA6yw2Va0FLa3Rguvbpa4W3I5xynaBZo41cM3XM+4Q6fRMj3sBYIR1VAmZMXYJvRQ==
   dependencies:
     tslib "^1.9.0"
 
+rxjs@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-7.0.0.tgz#c55d67c52aee8804d32ab60965e335bd41e2dc2d"
+  integrity sha512-I1V/ArAtGJg4kmCfms8fULm0SwYgEsAf2d5WPCBGzTYm2qTjO3Tx4EDFaGjbOox8CeEsC69jQK22mnmfyA26sw==
+  dependencies:
+    tslib "~2.1.0"
+
 safe-buffer@^5.1.0:
   version "5.2.1"
   resolved "https://registry.yarnpkg.com/safe-buffer/-/safe-buffer-5.2.1.tgz#1eaf9fa9bdb1fdd4ec75f58f9cdb4e6b7827eec6"
@@ -2376,6 +2383,11 @@ tslib@^2.0.0:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.2.0.tgz#fb2c475977e35e241311ede2693cee1ec6698f5c"
   integrity sha512-gS9GVHRU+RGn5KQM2rllAlR3dU6m7AcpJKdtH8gFvQiC4Otgk98XnmMU+nZenHt/+VhnBPWwgrJsyrdcw6i23w==
 
+tslib@~2.1.0:
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.1.0.tgz#da60860f1c2ecaa5703ab7d39bc05b6bf988b97a"
+  integrity sha512-hcVC3wYEziELGGmEEXue7D75zbwIIVUMWAVbHItGPx0ziyXxrOMQx4rQEVEV45Ut/1IotuEvwqPopzIOkDMf0A==
+
 tsutils-etc@^1.0.0, tsutils-etc@^1.3.3:
   version "1.3.3"
   resolved "https://registry.yarnpkg.com/tsutils-etc/-/tsutils-etc-1.3.3.tgz#02f115b373e87d315e90e8fdb561cb02427fac95"