context: bump gccgo-specific alloc limit for WithTimeout test.

9d8ef8d caused an extra allocation for gccgo.

Change-Id: I6568d84009882103ec4767546599afa20c54c480
Reviewed-on: https://go-review.googlesource.com/21940
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed