fix(demo): remove repetition id in demos (#3937)

Closes #3936

Author: tarusin

demo/src/app/docs/api-docs/api-doc-class/api-doc-class.component.html

@@ -7,7 +7,7 @@ <h3 [attr.id]="headerAnchor">
 
   <ng-template [ngIf]="apiDocs.properties && apiDocs.properties.length">
     <section>
-      <h3 id="inputs">Properties</h3>
+      <h3>Properties</h3>
       <table class="table table-bordered">
         <tbody>
         <tr *ngFor="let prop of apiDocs.properties">

demo/src/app/docs/api-docs/api-doc-config/api-doc-config.component.html

@@ -7,7 +7,7 @@ <h3 [attr.id]="headerAnchor">
 
   <ng-template [ngIf]="apiDocs.properties && apiDocs.properties.length">
     <section>
-      <h3 id="inputs">Properties</h3>
+      <h3>Properties</h3>
       <table class="table table-bordered">
         <tbody>
         <tr *ngFor="let prop of apiDocs.properties">

demo/src/app/docs/api-docs/api-doc/api-doc.component.html

@@ -22,7 +22,7 @@ <h3 [attr.id]="headerAnchor">
 
   <ng-template [ngIf]="apiDocs.inputs.length">
     <section>
-      <h3 id="inputs">Inputs</h3>
+      <h3>Inputs</h3>
       <div class="table-responsive">
         <table class="table table-bordered">
           <tbody>

demo/src/app/docs/api-docs/sample-box/sample-box.component.html

@@ -1,5 +1,5 @@
 <div class="section bd-example"><ng-content></ng-content></div>
-<div id="markup" class="section">
+<div class="section">
   <div class="item">
     <tabset>
       <tab heading="template" *ngIf="html">