gopls/internal/golang: splitlines: remove workaround for golang/go#68202

There's no need for splitlines to handle FuncDecl since it
handles FuncType... now that the bug in PathEnclosingInterval
is fixed.

Updates golang/go#68202

Change-Id: I3c96535b87c62e5d2a5b68ec66fed7df50b5d6c4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/595196
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>

Author: adonovan

gopls/internal/golang/lines.go

@@ -166,20 +166,8 @@ func findSplitJoinTarget(fset *token.FileSet, file *ast.File, src []byte, start,
 		path, _ := astutil.PathEnclosingInterval(file, start, end)
 		for _, node := range path {
 			switch node := node.(type) {
-			case *ast.FuncDecl:
-				// target struct method declarations.
-				//   function (...) someMethod(a int, b int, c int) (d int, e, int) {}
-				params := node.Type.Params
-				if isCursorInside(params.Opening, params.Closing) {
-					return "parameters", params, params.Opening, params.Closing
-				}
-
-				results := node.Type.Results
-				if results != nil && isCursorInside(results.Opening, results.Closing) {
-					return "results", results, results.Opening, results.Closing
-				}
 			case *ast.FuncType:
-				// target function signature args and result.
+				// target function signature parameters and results.
 				//   type someFunc func (a int, b int, c int) (d int, e int)
 				params := node.Params
 				if isCursorInside(params.Opening, params.Closing) {