Docs: consistent usage of CSS sections (#38175)

site/content/docs/5.3/components/dropdowns.md

@@ -1025,7 +1025,7 @@ Variables for the CSS-based carets that indicate a dropdown's interactivity:
 
 {{< scss-docs name="caret-variables" file="scss/_variables.scss" >}}
 
-### Mixins
+### Sass mixins
 
 Mixins are used to generate the CSS-based carets and can be found in `scss/mixins/_caret.scss`.
 

site/content/docs/5.3/components/modal.md

@@ -786,7 +786,7 @@ As part of Bootstrap's evolving CSS variables approach, modals now use local CSS
 
 {{< scss-docs name="modal-variables" file="scss/_variables.scss" >}}
 
-### Loop
+### Sass loop
 
 [Responsive fullscreen modals](#fullscreen-modal) are generated via the `$breakpoints` map and a loop in `scss/_modal.scss`.
 

site/content/docs/5.3/components/placeholders.md

@@ -138,8 +138,8 @@ Animate placeholders with `.placeholder-glow` or `.placeholder-wave` to better c
 </p>
 {{< /example >}}
 
-## Sass
+## CSS
 
-### Variables
+### Sass variables
 
 {{< scss-docs name="placeholders" file="scss/_variables.scss" >}}

site/content/docs/5.3/content/images.md

@@ -54,9 +54,9 @@ If you are using the `<picture>` element to specify multiple `<source>` elements
 </picture>
 ```
 
-## Sass
+## CSS
 
-### Variables
+### Sass variables
 
 Variables are available for image thumbnails.
 

site/content/docs/5.3/forms/floating-labels.md

@@ -173,8 +173,8 @@ When working with the Bootstrap grid system, be sure to place form elements with
 </div>
 {{< /example >}}
 
-## Sass
+## CSS
 
-### Variables
+### Sass variables
 
 {{< scss-docs name="form-floating-variables" file="scss/_variables.scss" >}}