[docs] Update MSSQL README

[colleenmcginnis]

Addresses feedback provided after #8240 was merged. See review comments: #8240 (review)

Proposed commit message

Update documentation

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• @colleenmcginnis address feedback
• @lalit-satapathy and/or @shmsr review

How to test this PR locally

View the README.

Related issues

Related to #8240

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-10-31T20:27:10.932+0000

• Duration: 70 min 35 sec

Test stats 🧪

Test	Results
Failed	0
Passed	19
Skipped	0
Total	19

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚
Classes	100.0% (2/2)	💚
Methods	93.75% (30/32)	❕
Lines	100.0% (1252/1252)	💚
Conditionals	100.0% (0/0)	💚

[shmsr]

Thanks!

[elasticmachine]

Package microsoft_sqlserver - 2.3.2 containing this change is available at https://epr.elastic.co/search?package=microsoft_sqlserver