docs(glossary): Pipes entry update (#3312)
docs(glossary): Pipes entry update (#3312)

Change Pipe glossary entry; it  used to suggested that one could
implemented a custom pipe by annotating a function with `@Pipe`.
chalin/angular.io,angular/angular-cn,angular/angular.io,angular/angular-cn,chalin/angular.io,IdeaBlade/angular.io,angular/angular-cn,IdeaBlade/angular.io,angular/angular.io,angular/angular-cn,angular/angular-cn,angular/angular.io,chalin/angular.io,IdeaBlade/angular.io,chalin/angular.io,chalin/angular.io,IdeaBlade/angular.io,angular/angular.io,angular/angular.io,IdeaBlade/angular.io