misc/cgo/testcshared: delete temporary directory in test
misc/cgo/testcshared: delete temporary directory in test

The deferred os.RemoveAll was accidentally committed as commented out
in the original https://golang.org/cl/87158.

Updates #30500

Change-Id: Idc5195816d7978253760dbfd78fde6d22c456296
Reviewed-on: https://go-review.googlesource.com/c/164858
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Daniel Martí <29bf28b42a938ace12a5819da4ed4ba03d82f315@mvdan.cc>

golang/go,golang/go,josharian/go,CAFxX/go,akutz/go,nawawi/go,CAFxX/go,josharian/go,golang/go,CAFxX/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,golang/go,golang/go,akutz/go,CAFxX/go,cloudflare/go,akutz/go,nawawi/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,akutz/go,golang/go,cloudflare/go,akutz/go,CAFxX/go,josharian/go,josharian/go,cloudflare/go,akutz/go,cloudflare/go,josharian/go,CAFxX/go,josharian/go,nawawi/go,cloudflare/go,nawawi/go,akutz/go,josharian/go,nawawi/go,CAFxX/go,nawawi/go,josharian/go,nawawi/go