Pre-existing gopls issues with line number changes should not be reported as regressions

-- p.go --
package p

func F() {
	x := 42
}

-- .commit --
Initial commit with existing gopls issue

-- p.go --
package p

// Change the line number of the unused variable

func F() {
	x := 42
}

-- .commit --
Add comments that change line numbers

-- .run_test --
OK