action.yml: make sure the latest Go version is default

Due to some confusion on the contract of one of the dependencies,
govulncheck-action would not by default try to download the newest go
version when one was present. This would sometimes even break the action
run due to a seemingly another issue with the dependency. This change
should fix both issues.

Fixes golang/go#69597

Change-Id: I51a21aad2daafc3984866051f91cf9339bb540e2
Reviewed-on: https://go-review.googlesource.com/c/govulncheck-action/+/616435
Reviewed-by: Maceo Thompson <maceothompson@google.com>
TryBot-Bypass: Zvonimir Pavlinovic <zpavlinovic@google.com>
Reviewed-by: Zvonimir Pavlinovic <zpavlinovic@google.com>

action.yml

@@ -1,13 +1,14 @@
 name: 'golang-govulncheck-action'
 description: 'Run govulncheck'
 inputs:
-  go-version-input:  # version of Go to use for govulncheck
+  go-version-input: # version of Go to use for govulncheck
     description: 'Version of Go to use for govulncheck'
     required: false
+    default: 'stable'
   check-latest:
     description: 'Set this option to true if you want the action to always check for the latest available Go version that satisfies the version spec'
     required: false
-    default: false
+    default: true
   cache:
     description: 'Used to specify whether Go caching is needed. Set to true, if you would like to enable caching.'
     required: false