minor #809 [Doc] typo(index): small fix (Guikingone)

This PR was merged into the 2.x branch.

Discussion
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[Doc] typo(index): small fix

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Tickets       | Fix #...
| License       | MIT

Just noticed this `if` in the sentence, might be wrong but perhaps `is` will be better? 🤔

Commits
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1834cdc typo(index): small fix

Author: weaverryan

src/LiveComponent/doc/index.rst

@@ -2669,7 +2669,7 @@ Advanced Functionality
 The Smart Re-Render Algorithm
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-When a component re-renders, the new HTML if "morphed" onto the existing
+When a component re-renders, the new HTML is "morphed" onto the existing
 elements on the page. For example, if the re-render includes a new ``class``
 on an existing element, that class will be added to that element.