gopls/internal/settings: remove MemoryMode option

It has had no effect for some time.

Fixes golang/go#46902

Change-Id: I429121614a00210cc1053d2031eeb994de18e02c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/548739
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

gopls/doc/settings.md

@@ -85,23 +85,13 @@ is the part of the file name after the final dot.)
 
 Default: `[]`.
 
-#### **memoryMode** *enum*
+#### **memoryMode** *string*
 
 **This setting is experimental and may be deleted.**
 
-memoryMode controls the tradeoff `gopls` makes between memory usage and
-correctness.
+obsolete, no effect
 
-Values other than `Normal` are untested and may break in surprising ways.
-
-Must be one of:
-
-* `"DegradeClosed"`: In DegradeClosed mode, `gopls` will collect less information about
-packages without open files. As a result, features like Find
-References and Rename will miss results in such packages.
-* `"Normal"`
-
-Default: `"Normal"`.
+Default: `""`.
 
 #### **expandWorkspaceToModule** *bool*
 

gopls/internal/settings/default.go

@@ -62,7 +62,6 @@ func DefaultOptions(overrides ...func(*Options)) *Options {
 			UserOptions: UserOptions{
 				BuildOptions: BuildOptions{
 					ExpandWorkspaceToModule: true,
-					MemoryMode:              ModeNormal,
 					DirectoryFilters:        []string{"-**/node_modules"},
 					TemplateExtensions:      []string{},
 					StandaloneTags:          []string{"ignore"},

gopls/internal/settings/settings.go

@@ -175,11 +175,8 @@ type BuildOptions struct {
 	// is the part of the file name after the final dot.)
 	TemplateExtensions []string
 
-	// MemoryMode controls the tradeoff `gopls` makes between memory usage and
-	// correctness.
-	//
-	// Values other than `Normal` are untested and may break in surprising ways.
-	MemoryMode MemoryMode `status:"experimental"`
+	// obsolete, no effect
+	MemoryMode string `status:"experimental"`
 
 	// ExpandWorkspaceToModule instructs `gopls` to adjust the scope of the
 	// workspace to find the best available module root. `gopls` first looks for
@@ -661,16 +658,6 @@ const (
 	Structured HoverKind = "Structured"
 )
 
-type MemoryMode string
-
-const (
-	ModeNormal MemoryMode = "Normal"
-	// In DegradeClosed mode, `gopls` will collect less information about
-	// packages without open files. As a result, features like Find
-	// References and Rename will miss results in such packages.
-	ModeDegradeClosed MemoryMode = "DegradeClosed"
-)
-
 type VulncheckMode string
 
 const (
@@ -941,12 +928,7 @@ func (o *Options) set(name string, value interface{}, seen map[string]struct{})
 		o.DirectoryFilters = filters
 
 	case "memoryMode":
-		if s, ok := result.asOneOf(
-			string(ModeNormal),
-			string(ModeDegradeClosed),
-		); ok {
-			o.MemoryMode = MemoryMode(s)
-		}
+		result.deprecated("")
 	case "completionDocumentation":
 		result.setBool(&o.CompletionDocumentation)
 	case "usePlaceholders":