[DOCS] Update Template Link in Create a Custom Batch Expectation

[kwcanuck]

In DOC-702, a user indicated the link to the custom BatchExpectation template returned a 404 error. This PR updates the link so it functions correctly.

Definition of done

• PR title is prefixed with one of: [BUGFIX], [FEATURE], [DOCS], [MAINTENANCE], [CONTRIB]
• Appropriate tests and docs have been updated

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.64%. Comparing base (c9e492a) to head (902f28d).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #9731   +/-   ##
========================================
  Coverage    82.64%   82.64%           
========================================
  Files          512      512           
  Lines        46648    46648           
========================================
  Hits         38554    38554           
  Misses        8094     8094           

Flag	Coverage Δ
3.10	64.89% <ø> (ø)
3.11	64.89% <ø> (ø)
3.11 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	53.87% <ø> (ø)
3.11 aws_deps	48.95% <ø> (ø)
3.11 big	64.13% <ø> (ø)
3.11 databricks	48.14% <ø> (ø)
3.11 filesystem	63.79% <ø> (ø)
3.11 mssql	47.36% <ø> (ø)
3.11 mysql	47.41% <ø> (ø)
3.11 postgresql	54.16% <ø> (ø)
3.11 snowflake	48.66% <ø> (-0.01%)	⬇️
3.11 spark	60.57% <ø> (ø)
3.11 trino	53.79% <ø> (ø)
3.8	64.90% <ø> (ø)
3.8 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	53.87% <ø> (ø)
3.8 aws_deps	48.96% <ø> (ø)
3.8 big	64.13% <ø> (ø)
3.8 databricks	48.15% <ø> (ø)
3.8 filesystem	63.79% <ø> (ø)
3.8 mssql	47.34% <ø> (ø)
3.8 mysql	47.39% <ø> (ø)
3.8 postgresql	54.15% <ø> (ø)
3.8 snowflake	48.68% <ø> (-0.01%)	⬇️
3.8 spark	60.53% <ø> (ø)
3.8 trino	53.78% <ø> (ø)
3.9	64.90% <ø> (+0.01%)	⬆️
cloud	0.00% <ø> (ø)
docs-basic	54.44% <ø> (ø)
docs-creds-needed	55.01% <ø> (ø)
docs-spark	54.54% <ø> (ø)

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[Rachel-Reverie]

LGTM