docs(nrql_alert_condition.html.markdown): fix example

[mvdiener]

Description

Update the docs to use a valid example.

Fixes #
Trying to use the previous example gives errors about invalid Handlebars. This updates the docs example to a valid Handlebars statement.

Type of change

• This change requires a documentation update

Checklist:

Please delete options that are not relevant.

• I have made corresponding changes to the documentation

How to test this change?

Only docs changes.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.06%. Comparing base (92361de) to head (77ecd38).
Report is 132 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2793      +/-   ##
==========================================
- Coverage   32.82%   31.06%   -1.76%     
==========================================
  Files          98      102       +4     
  Lines       26884    27602     +718     
==========================================
- Hits         8824     8574     -250     
- Misses      17902    18858     +956     
- Partials      158      170      +12     

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[vinay-newrelic]

Approved