go.tools/go/types: enable float_lit2.go test

Pending CL 91590047 which fixes that test.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/91630043

go/types/stdlib_test.go

@@ -119,7 +119,6 @@ func TestStdTest(t *testing.T) {
 	testTestDir(t, filepath.Join(runtime.GOROOT(), "test"),
 		"cmplxdivide.go", // also needs file cmplxdivide1.go - ignore
 		"sigchld.go",     // don't work on Windows; testTestDir should consult build tags
-		"float_lit2.go",  // TODO(gri) 340282356779733661637539395458142568447 not representable as float32
 	)
 }