update cache miss to warning from error (#7657)

NAA customer request to update cache miss as warning in logs instead of
error. Having `error` in log is confusing since the token request
proceeds without throwing.

Author: sameerag

Diff for: change/@azure-msal-browser-b8331fbd-7e54-4c81-9dbf-d133b23b93bb.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "update cache miss to warning from error",
+  "packageName": "@azure/msal-browser",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

Diff for: lib/msal-browser/src/controllers/NestedAppAuthController.ts

@@ -437,7 +437,7 @@ export class NestedAppAuthController implements IController {
             return result;
         }
 
-        this.logger.error(
+        this.logger.warning(
             "Cached tokens are not found for the account, proceeding with silent token request."
         );