cmd/guru: remove test assertions involving unsafe to fix the build

Go 1.17 adds the unsafe.Add and unsafe.Slice functions, which causes the
guru describe assertions about unsafe to either fail at 1.17 or fail at
earlier Go versions.

This is causing the longtest builds to break.

Remove them for now. If we remember, we can add them back once we no
longer support 1.16.

Fixes golang/go#45778

Change-Id: Ie72355fbab8e614c0150097c84c796e78d968839
Reviewed-on: https://go-review.googlesource.com/c/tools/+/313251
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: findleyr

cmd/guru/testdata/src/describe/main.go

@@ -10,7 +10,10 @@ import (
 	"lib"
 	"nosuchpkg"            // @describe badimport1 "nosuchpkg"
 	nosuchpkg2 "nosuchpkg" // @describe badimport2 "nosuchpkg2"
-	_ "unsafe"             // @describe unsafe "unsafe"
+	// The unsafe package changed in Go 1.17 with the addition of
+	// unsafe.Add and unsafe.Slice. While we still support older versions
+	// of Go, the test case below cannot be enabled.
+	// _ "unsafe"             // @describe unsafe "unsafe"
 )
 
 var _ nosuchpkg.T

cmd/guru/testdata/src/describe/main.golden

@@ -20,13 +20,6 @@ import of package "nosuchpkg"
 -------- @describe badimport2 --------
 reference to package "nosuchpkg"
 
--------- @describe unsafe --------
-import of package "unsafe"
-	builtin Alignof 
-	builtin Offsetof
-	type  Pointer  unsafe.Pointer
-	builtin Sizeof  
-
 -------- @describe type-ref-builtin --------
 reference to built-in type float64