README: don't mention the Go version required for the action

The desired Go version is almost always dictated by Staticcheck, not the
action. And while the action still supports very old versions of Go,
nobody should be using those anymore. Remove mention of the action's
requirement to avoid confusion.

Closes: gh-10

README.md

@@ -93,7 +93,6 @@ If Staticcheck is the only action in your job, this option can usually be left o
 If your job already installs Go prior to running Staticcheck, for example to run unit tests, it is best to set this option to `false`.
 
 The latest release of Staticcheck works with the last minor release of Go at the time.
-The action itself requires at least Go 1.16.
 
 ### `cache-key`