fix (inputs/mongodb) readme: correct connection URI

[anti32]

Required for all PRs:

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format

Since v1.19.2 telegraf collects PRIMARY MongoDB metrics via SECONDARY servers by default. By that it means you are not able to get SECONDARY server metrics with default configuration. To fix that, ?connection=direct should be used in conection string URL. Hopefully that README.md fix saves lot of debugging time in future for other users :))

[telegraf-tiger]

Thanks so much for the pull request!
🤝 ✒️ Just a reminder that the CLA has not yet been signed, and we'll need it before merging. Please sign the CLA when you get a chance, then post a comment here saying !signed-cla

[anti32]

!signed-cla

[telegraf-tiger]

😄 This pull request doesn't change the Telegraf binary size

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Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armel.deb	armv6hl.rpm	freebsd_armv7.tar.gz
armhf.deb	i386.rpm	freebsd_i386.tar.gz
i386.deb	ppc64le.rpm	linux_amd64.tar.gz
mips.deb	s390x.rpm	linux_arm64.tar.gz
mipsel.deb	x86_64.rpm	linux_armel.tar.gz
ppc64el.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_s390x.tar.gz
		static_linux_amd64.tar.gz

[sspaink]

Thanks for updating the docs! Is there a documentation link you could add where you found this correct URL? Maybe it would help users as well.

[sspaink]

Don't worry about the linter failure in the checks, it checks the entire file not just the parts you changed. I went ahead and resolved the linter issues in a separate PR: #10077

[anti32]

I found that correct URL after few days debugging and compiling. Final answer was found somewhere from Golang MongoDB driver source code

[sspaink]

Found this relevant stackoverflow question: https://stackoverflow.com/questions/60765600/why-isnt-connect-option-in-mongo-connection-string-documented

Looks like it is only documented in the MongoDB Go Driver, because its only supported there at the moment: https://pkg.go.dev/go.mongodb.org/mongo-driver/mongo?utm_source=godoc#example-Connect-Direct

Not sure how helpful adding that link to the document would be, just updating the example URL like you did probably will suffice. Thanks!