Remove extra mentions of gap shim (#5361)

Author: LFDanLu

NOTICE.txt

@@ -47,14 +47,6 @@ This codebase contains a portion of code from react which can be obtained at:
     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     SOFTWARE.
 
--------------------------------------------------------------------------------
-This codebase contains a modified portion of code from Modernizr which can be obtained at:
-  * SOURCE:
-    * https://github.com/Modernizr/Modernizr/blob/7efb9d0edd66815fb115fdce95fabaf019ce8db5/feature-detects/css/flexgap.js
-
-  * LICENSE:
-    * https://github.com/Modernizr/Modernizr/blob/master/LICENSE
-
 -------------------------------------------------------------------------------
 This codebase contains a modified portion of code from react-window which can be obtained at:
   * SOURCE:

packages/dev/docs/pages/react-spectrum/layout.mdx

@@ -61,9 +61,7 @@ component can be used to create flexbox containers, and any React Spectrum compo
 Flex layouts are also automatically mirrored in right-to-left languages, and can be nested to create
 more complex layouts.
 
-In addition to the properties widely supported by CSS, React Spectrum also shims the `gap` property, along
-with `rowGap` and `columnGap`. These properties make it much easier to build layouts
-with consistent space between each item. The gap can be defined with [Spectrum dimension variables](styling.html#dimension-values)
+The `gap`, `rowGap` and `columnGap` can be defined with [Spectrum dimension variables](styling.html#dimension-values)
 to ensure consistency across applications, and allow the layout to adapt to different devices automatically.
 
 ### Example