Typo fix (#1803)

* Update text_options.rs

* Update src/schema/text_options.rs

Co-authored-by: Paul Masurel <paul@quickwit.io>

src/schema/text_options.rs

@@ -30,7 +30,7 @@ impl TextOptions {
         self.stored
     }
 
-    /// Returns true iff the value is a fast field.
+    /// Returns true if and only if the value is a fast field.
     pub fn is_fast(&self) -> bool {
         self.fast
     }