docs(architecture): minor adjustments (#2994)
docs(architecture): minor adjustments (#2994)

Minor adjustments, in particular, gets rid of custom styling in favor
of using plain markdown for pipe example. This fixes the layout for
some displays.

Followup to #2990
onyoon7/angular-ko,angular/angular-cn,onyoon7/angular-ko,Urigo/angular.io,angular/angular-ko,rsreimer/angular.io,chalin/angular.io,angular/angular-cn,IdeaBlade/angular.io,angular/angular-ko,IdeaBlade/angular.io,angular/angular.io,angular/angular-ko,onyoon7/angular-ko,angular/angular.io,Urigo/angular.io,angular/angular.io,onyoon7/angular-ko,angular/angular.io,rsreimer/angular.io,angular/angular.io,Urigo/angular.io,Urigo/angular.io,onyoon7/angular-ko,angular/angular-ko,IdeaBlade/angular.io,rsreimer/angular.io,angular/angular-ko,Urigo/angular.io,juleskremer/angular.io,chalin/angular.io,rsreimer/angular.io,IdeaBlade/angular.io,juleskremer/angular.io,chalin/angular.io,realappie/angular.io,angular/angular-cn,angular/angular-cn,realappie/angular.io,juleskremer/angular.io,realappie/angular.io,realappie/angular.io,chalin/angular.io,IdeaBlade/angular.io,rsreimer/angular.io,angular/angular-cn,juleskremer/angular.io,juleskremer/angular.io,realappie/angular.io,chalin/angular.io