Update README config sect to match default values

In particular, the configuration section, as well as the section
discussing the handling of unhandled rejections, discussed the
default behavior of handling unhandled rejections.  Now the
default action is not described in the configuration section so
that only one section describes that behavior.

packages/error-reporting/README.md

@@ -165,8 +165,8 @@ var errors = require('@google-cloud/error-reporting')({
   // defaults to 2 (warnings)
   logLevel: 2,
   // determines whether or not unhandled rejections are reported to the
-  // error-reporting console.  The default value of this property is true.
-  reportUnhandledRejections: false,
+  // error-reporting console
+  reportUnhandledRejections: true,
   serviceContext: {
       service: 'my-service',
       version: 'my-service-version'