fix(curriculum): grammatical errors (freeCodeCamp#49537)

* Minor grammatical change 

```diff
# --description--
-      Create an .small-text selector and set the font-size to 0.85rem, which would calculate to be roughly 13.6px (remember that you set your html to have a font-size of 16px).
+      Create a .small-text selector and set the font-size to 0.85rem, which would calculate to roughly 13.6px (remember that you set your html to have a font-size of 16px).
```

* Add backticks for formatting purposes

Co-authored-by: Krzysztof G. <60067306+gikf@users.noreply.github.com>

---------

Co-authored-by: Krzysztof G. <60067306+gikf@users.noreply.github.com>

Author: Hacktinium

curriculum/challenges/english/14-responsive-web-design-22/learn-typography-by-building-a-nutrition-label/615f522dea4f776f64dc3e91.md

@@ -9,7 +9,7 @@ dashedName: step-31
 
 The `rem` unit stands for `root em`, and is relative to the font size of the `html` element.
 
-Create an `.small-text` selector and set the `font-size` to `0.85rem`, which would calculate to be roughly `13.6px` (remember that you set your `html` to have a `font-size` of `16px`).
+Create a `.small-text` selector and set the `font-size` to `0.85rem`, which would calculate to roughly `13.6px` (remember that you set your `html` to have a `font-size` of `16px`).
 
 # --hints--