docs: Minor range example code optimization (#41665)

I think the 'custom' prefix for the ids in examples were mainly from Bootstrap v4 custom controls. Removing it makes it a bit shorter/neater.

Author: coliff

site/src/content/docs/forms/range.mdx

@@ -8,8 +8,8 @@ toc: true
 
 Create custom `<input type="range">` controls with `.form-range`. The track (the background) and thumb (the value) are both styled to appear the same across browsers. As only Firefox supports “filling” their track from the left or right of the thumb as a means to visually indicate progress, we do not currently support it.
 
-<Example code={`<label for="customRange1" class="form-label">Example range</label>
-<input type="range" class="form-range" id="customRange1">`} />
+<Example code={`<label for="range1" class="form-label">Example range</label>
+<input type="range" class="form-range" id="range1">`} />
 
 ## Disabled
 
@@ -22,27 +22,27 @@ Add the `disabled` boolean attribute on an input to give it a grayed out appeara
 
 Range inputs have implicit values for `min` and `max`—`0` and `100`, respectively. You may specify new values for those using the `min` and `max` attributes.
 
-<Example code={`<label for="customRange2" class="form-label">Example range</label>
-<input type="range" class="form-range" min="0" max="5" id="customRange2">`} />
+<Example code={`<label for="range2" class="form-label">Example range</label>
+<input type="range" class="form-range" min="0" max="5" id="range2">`} />
 
 ## Steps
 
 By default, range inputs “snap” to integer values. To change this, you can specify a `step` value. In the example below, we double the number of steps by using `step="0.5"`.
 
-<Example code={`<label for="customRange3" class="form-label">Example range</label>
-<input type="range" class="form-range" min="0" max="5" step="0.5" id="customRange3">`} />
+<Example code={`<label for="range3" class="form-label">Example range</label>
+<input type="range" class="form-range" min="0" max="5" step="0.5" id="range3">`} />
 
 ## Output value
 
 The value of the range input can be shown using the `output` element and a bit of JavaScript.
 
-<Example code={`<label for="customRange4" class="form-label">Example range</label>
-  <input type="range" class="form-range" min="0" max="100" value="50" id="customRange4">
-  <output for="customRange4" id="rangeValue" aria-hidden="true"></output>
+<Example code={`<label for="range4" class="form-label">Example range</label>
+  <input type="range" class="form-range" min="0" max="100" value="50" id="range4">
+  <output for="range4" id="rangeValue" aria-hidden="true"></output>
 
   <script>
     // This is an example script, please modify as needed
-    const rangeInput = document.getElementById('customRange4');
+    const rangeInput = document.getElementById('range4');
     const rangeOutput = document.getElementById('rangeValue');
 
     // Set initial value