Bump RC version to 19.0.0-rc.1 (#31542)

Author: acdlite

ReactVersions.js

@@ -30,7 +30,7 @@ const canaryChannelLabel = 'rc';
 
 // If the canaryChannelLabel is "rc", the build pipeline will use this to build
 // an RC version of the packages.
-const rcNumber = 0;
+const rcNumber = 1;
 
 const stablePackages = {
   'eslint-plugin-react-hooks': '5.1.0',