Prevent the error when explicitly specifying default buf gen temlate file path

[un1024]

Backgroud: I encountered the following error.

Buf gen template file specified in the project directory as well as with templateFileLocation; pick one.

But I have just one template file {rootDir}/buf.gen.yaml.
I didn't understand the reason for the error until I read the source code.

I think it's natural to want to specify the file path explicitly.
Therefore how about making this trivial fix to prevent confusion?

Thanks.

[CLAassistant]

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