docs: [no-floating-promises] fix capitalization typo (typescript-eslint#9118)

capialization typo

Co-authored-by: Joshua Chen <[email protected]>

Author: kirkwaiblinger

Diff for: packages/eslint-plugin/docs/rules/no-floating-promises.mdx

@@ -100,7 +100,7 @@ With this option set to `true`, and if you are using `no-void`, you should turn
 
 ### `ignoreIIFE`
 
-This allows you to skip checking of async IIFEs (Immediately Invoked function Expressions).
+This allows you to skip checking of async IIFEs (Immediately Invoked Function Expressions).
 
 Examples of **correct** code for this rule with `{ ignoreIIFE: true }`: