internal/lsp/mod: fix test that checks for unchanged go.mod
internal/lsp/mod: fix test that checks for unchanged go.mod

The test that checks to make sure a user's go.mod file does not change if tempModfile=true is not doing anything. At some point, the go.mod file to test added a go directive. This change removes the go directive from the go.mod file.

Change-Id: I1c4b6b326e99d8fec5c21ac779dcdcd73610f48c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/216840
Run-TryBot: Rohan Challa <9671c73253cee9b18b8df367e3e627fab2863fe8@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>

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