Correct a typological error in credentials/ec2rolecreds/doc.go

[ebi-yade]

Hello maintainer-san, 👋🏽

I have just come across the error in Go doc!
The project does not appear to have the same typos as this one.
I am afraid to request a review for such a trivial change, but could you please take a look at this?

$ grep -r ' int he '
./credentials/ec2rolecreds/doc.go:// credential provider int he credential chain if no other credential provider is