go/ssa: more reindentation of TestGenericBodies

This was split into two parts to be easier to review in gerrit.

Change-Id: Ie308e06d9c49836f49451006075a3d6fd10cfaee
Reviewed-on: https://go-review.googlesource.com/c/tools/+/493057
Reviewed-by: Alan Donovan <[email protected]>
Run-TryBot: Tim King <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
gopls-CI: kokoro <[email protected]>

Author: timothy-king