entc/gen: mark field as cleared when clearing edges (#3651)

* mark field as cleared when clearing edges

* regenerate examples

* run go generate in entc/integration

* runn go mod tidy

entc/gen/template/builder/mutation.tmpl

@@ -329,6 +329,10 @@ func (m {{ $mutation }}) Tx() (*Tx, error) {
 	// {{ $func }} clears the "{{ $e.Name }}" edge to the {{ $e.Type.Name }} entity.
 	func (m *{{ $mutation }}) {{ $func }}() {
 		m.cleared{{ $e.BuilderField }} = true
+		{{- if $e.Field }}
+			{{- $const := print $n.Package "." $e.Field.Constant }}
+			m.clearedFields[{{ $const }}] = struct{}{}
+		{{- end }}
 	}
 
 	{{ $func = $e.MutationCleared }}
@@ -753,4 +757,4 @@ func (m *{{ $mutation }}) ResetEdge(name string) error {
 }
 {{ end }}
 
-{{ end }}
+{{ end }}