UX: Remove Helvetica from our font stack (#11876)

Arial is more consistently available across operating systems and aligns better.

app/assets/javascripts/discourse/app/lib/update-tab-count.js

@@ -18,7 +18,7 @@ function renderIcon(canvas, img, count) {
 
   canvas.height = canvas.width = img.width;
   let ctx = canvas.getContext("2d");
-  ctx.font = `bold ${fontSize}px Helvetica, Arial, sans-serif`;
+  ctx.font = `bold ${fontSize}px Arial, sans-serif`;
 
   if (count) {
     ctx.globalAlpha = 0.4;

app/assets/stylesheets/common/base/username_tagsinput.scss

@@ -19,7 +19,6 @@ div.tagsinput span.tag {
   color: #638421;
   margin-right: 5px;
   margin-bottom: 5px;
-  font-family: helvetica;
   font-size: $font-down-1;
 }
 
@@ -31,7 +30,6 @@ div.tagsinput span.tag a {
 }
 div.tagsinput input {
   width: 80px;
-  font-family: helvetica;
   font-size: $font-down-1;
   border: 1px solid transparent;
   padding: 2px 5px;

app/assets/stylesheets/vendor/pikaday.scss

@@ -28,7 +28,7 @@ $pd-day-disabled-color: var(--primary) !default;
 $pd-week-color: var(--primary) !default;
 
 // Font
-$pd-font-family: "Helvetica Neue", Helvetica, Arial, sans-serif !default;
+$pd-font-family: Arial, sans-serif !default;
 
 
 .pika-single {

app/assets/stylesheets/wizard.scss

@@ -714,7 +714,7 @@ body.wizard {
   line-height: $line-height-large;
   font-size: 15px;
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
-    Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
+    Oxygen-Sans, Ubuntu, Cantarell, Arial, sans-serif;
 
   #wizard-main {
     display: flex;