Remove unused TypeInfo.Identifier()

atree.TypeInfo interface used to include Identifier() function.
However, Identifier() was removed later and is no longer part of
atree.TypeInfo interface.

This commit removes Identifier() function from structs
implementing atree.TypeInfo interface.

Author: fxamacker

interpreter/encode.go

@@ -1684,10 +1684,6 @@ func (c compositeTypeInfo) IsComposite() bool {
 	return true
 }
 
-func (c compositeTypeInfo) Identifier() string {
-	return string(c.location.TypeID(nil, c.qualifiedIdentifier))
-}
-
 func (c compositeTypeInfo) Copy() atree.TypeInfo {
 	// Return c as is because c is a value type.
 	return c
@@ -1741,10 +1737,6 @@ func (e EmptyTypeInfo) IsComposite() bool {
 	return false
 }
 
-func (e EmptyTypeInfo) Identifier() string {
-	return ""
-}
-
 func (e EmptyTypeInfo) Copy() atree.TypeInfo {
 	return e
 }

interpreter/statictype.go

@@ -252,10 +252,6 @@ func (t *VariableSizedStaticType) Copy() atree.TypeInfo {
 	return t
 }
 
-func (t *VariableSizedStaticType) Identifier() string {
-	return string(t.ID())
-}
-
 func (*VariableSizedStaticType) isStaticType() {}
 
 func (*VariableSizedStaticType) elementSize() uint {
@@ -382,10 +378,6 @@ func (t *ConstantSizedStaticType) Copy() atree.TypeInfo {
 	return t
 }
 
-func (t *ConstantSizedStaticType) Identifier() string {
-	return string(t.ID())
-}
-
 func (*ConstantSizedStaticType) isStaticType() {}
 
 func (*ConstantSizedStaticType) elementSize() uint {
@@ -464,10 +456,6 @@ func (t *DictionaryStaticType) Copy() atree.TypeInfo {
 	return t
 }
 
-func (t *DictionaryStaticType) Identifier() string {
-	return string(t.ID())
-}
-
 func (*DictionaryStaticType) isStaticType() {}
 
 func (*DictionaryStaticType) elementSize() uint {