Passed buffer as 0 to fix extra gap in EuiSuperSelect (#3685)

* Passed buffer as 0 to fix extra gap in superselect

* Updated changelog

* Improving changelog

* Snapshots

Co-authored-by: miukimiu <elizabet.oliveira@elastic.co>

CHANGELOG.md

@@ -18,6 +18,7 @@ No public interface changes since `26.2.0`.
 - Fixed `EuiSkipLink` interactive props and Safari click issue ([#3665](https://github.com/elastic/eui/pull/3665))
 - Fixed `z-index` issues with `EuiHeader`, `EuiFlyout`, and other portal content ([#3655](https://github.com/elastic/eui/pull/3655))
 - Fixed `color` prop error in `EuiBadge` to be more flexible with what format it accepts ([#3655](https://github.com/elastic/eui/pull/3655))
+- Fixed `EuiSuperSelect` popover from moving 16px horizontally when it's close to a window edge ([#3685](https://github.com/elastic/eui/pull/3685))
 
 **Theme: Amsterdam**
 

src/components/color_picker/color_palette_picker/__snapshots__/color_palette_picker.test.tsx.snap

@@ -591,6 +591,7 @@ exports[`EuiColorPalettePicker more props are propagated to each option 2`] = `
   >
     <EuiPopover
       anchorPosition="downCenter"
+      buffer={0}
       button={
         <EuiSuperSelectControl
           className="euiSuperSelect--isOpen__button"

src/components/form/super_select/__snapshots__/super_select.test.tsx.snap

@@ -530,6 +530,7 @@ exports[`EuiSuperSelect props more props are propogated to each option 2`] = `
 >
   <EuiPopover
     anchorPosition="downCenter"
+    buffer={0}
     button={
       <EuiSuperSelectControl
         className="euiSuperSelect--isOpen__button"

src/components/form/super_select/super_select.tsx

@@ -339,7 +339,8 @@ export class EuiSuperSelect<T extends string> extends Component<
         anchorPosition="downCenter"
         ownFocus={false}
         popoverRef={this.setPopoverRef}
-        hasArrow={false}>
+        hasArrow={false}
+        buffer={0}>
         <EuiScreenReaderOnly>
           <p role="alert">
             <EuiI18n