Added description for the -v --validate flag in Command Line Notes table in token.md

[constantstress]

Added --validate / -v flag to command line notes table

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Problem/Feature

Command Line Notes table in token.md file in documentation was missing description for v validate flag

Description of Changes:

• I added this description. Values for Description and Example table fields were taken from the source code of cmd/token.go file

Checklist

• My code follows the Contribution Guide
• I have self-reviewed the changes being requested
• I have made comments on pieces of code that may be difficult to understand for other editors
• I have updated the documentation (if applicable)