internal/bytealg: fix typo in IndexRabinKarp{,Bytes} godoc
internal/bytealg: fix typo in IndexRabinKarp{,Bytes} godoc

Change-Id: I09ba19e19b195e345a0fe29d542e0d86529b0d31
Reviewed-on: https://go-review.googlesource.com/c/go/+/261359
Trust: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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