Changing number to string in example yaml

[SHA65536]

This example shows supplying go-version as a number 1.15, this works for version up to 1.19, but with 1.20, it will turn it into a number (1.2) and then back into a string "1.2" making the action use Go 1.2 instead of 1.20.

Why:

I saw someone face this issue and realized the problem came from this example on the docs.

Closes: #25145

What's being changed (if available, include any code snippets, screenshots, or gifs):

Go version type from 1.5 to '1.5' to prevent wrong version after conversion to number.

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Source	Preview	Production	What Changed
actions/automating-builds-and-tests/building-and-testing-go.md	fpt ghec ghes@ 3.8 3.7 3.6 3.5 3.4 ghae	fpt ghec ghes@ 3.8 3.7 3.6 3.5 3.4 ghae

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ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server
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[cmwilson21]

@SHA65536 Thank you for opening a PR and linking it to your issue! ✨

I'll get this triaged for review! ⚡

[skedwards88]

Thanks for fixing this! We'll get this merged down for you.

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