gopls/internal/regtest: re-enable the gc_details regtest for -short
gopls/internal/regtest: re-enable the gc_details regtest for -short

My hope is that CL 304169 resolved this flake, but we'll have to see.

For golang/go#44099

Change-Id: Iac82dc24167daacd0361eac1a5567048a7ecf11c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/305409
Trust: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
Run-TryBot: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools