fix typo in Acknowledgements section

[kwatsen]

Issues closed

Please list all the issues this PR closes.
The issues will auto-close when the PR merges.
Syntax follows:

Closes #?? // for issues in the yang-xml repo
Closes netmod-wg/yang-next#?? // for YANG-next issues
None // if PR doesn't close an issue

Design

Please indicate if a design was created for this PR and, if so,
a link to it. Either:

None
https://github.com/netmod-wg/yang-xml/designs/\<filename>

Additional Information

Any additional information that would not go into the an Issue or the draft itself?
If no Issue is listed above, please fill this section in...

[github-actions]

All of the following must be verified before merging to main.

• Updated "IANA Considerations" section, or N/A?
• Updated "Security Considerations" section, or N/A?
• Updated "Normative/Informational References" sections, or N/A?
• Updated "Acknowledgements" section, or N/A? (Not GitHub users)