reflect: remove unused overflowPad variable
reflect: remove unused overflowPad variable

overflowPad variable in bucketOf function is a holdover from a NaCl port
and never used now.

Change-Id: Ib68fdb054e1b6a655ffbfd34521a3f8773a22694
GitHub-Last-Rev: f281be9c115a87605fd28b39c0b09eed54cc774a
GitHub-Pull-Request: golang/go#52449
Reviewed-on: https://go-review.googlesource.com/c/go/+/401274
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
Auto-Submit: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@google.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>

golang/go,golang/go,golang/go,nawawi/go,nawawi/go,nawawi/go,golang/go,nawawi/go,golang/go,golang/go,nawawi/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go