Note: Doc team updates the current version of the documentation and the
two previous versions (n-2), but we address *only high-priority, or
customer-reported issues* for -2 releases in support.
Describe the changes in the doc and link to your dev story:

1. - [x] Mandatory: Add the required version to the Fix version/s field.

2. - [x] Mandatory: Choose the type of documentation change or review.

• [x] We need to update to an existing topic

• [ ] We need to add a new document to an existing section

• [ ] We need a whole new section; this is a function not
  documented before and doesn't belong in any current section

• [ ] We need an Operator Advisory review and approval

• [ ] We need a z-Stream (Errata) Advisory and Release note for
  MCE and/or ACM

3. - [x] Mandatory: Find the link to where the documentation update
should go and add it to the recommended changes. You can either use the
published doc or the staged repo for this step:

The currently published doc is https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.15/html-single/governance/index#open-source-community-functions

The spot in the stage repo is https://github.com/stolostron/rhacm-docs/blob/2.16_stage/governance/template_functions.adoc#sprig-open-source

4. - [x] Mandatory for GA content:

• [x] Add steps, the diff, known issue, and/or other important
  conceptual information in the following space:

Previously we had a list of allowed sprig functions. We had often been asked to include more. Now we have a denylist, with only two functions currently not allowed in templates: `env` and `expandenv`. These functions are denied because they are potentially security concerns.

• [ ] *Add Required access level *(example, *Cluster
  Administrator*) for the user to complete the task:

• [ ] Add verification at the end of the task, how does the user
  verify success (a command to run or a result to see?)

• [x] Add link to dev story here: https://issues.redhat.com/browse/ACM-27751 

5. - [x] Mandatory for bugs: What is the diff? Clearly define what the
problem is, what the change is, and link to the current documentation. Only
use this for a documentation bug.

Basically I just want to adjust the doc to note that all sprig functions are now available, including the ones we already have listed there, but I don't think we need to necessarily add additional functions into the table - linking to the open source Sprig repository is sufficient (and we already do that).