[Security Solution][Bug] Fixes visual issue in Safari (#165377)

## Summary

Fixes issue in descriptions of landing page icons which were always
displaying in white color. It only happens in Safari, other browsers
show the text in the correct color.

Fix: Remove misuse of `color` property in `EuiText` component

Before:


![before](ff03272f-3f2b-4d32-a10f-8b223a7c80c8)

After:


![after](6ae6f235-4572-4ee7-9103-377869567a35)

x-pack/packages/security-solution/navigation/src/landing_links/landing_links_icons.tsx

@@ -81,9 +81,7 @@ export const LandingLinkIcon: React.FC<LandingLinkIconProps> = React.memo(functi
         </EuiTitle>
       </EuiFlexItem>
       <EuiFlexItem grow={false} css={styles.description}>
-        <EuiText size="s" color="text">
-          {description}
-        </EuiText>
+        <EuiText size="s">{description}</EuiText>
       </EuiFlexItem>
       <EuiFlexItem>{children}</EuiFlexItem>
     </EuiFlexGroup>

x-pack/packages/security-solution/navigation/src/landing_links/landing_links_images.tsx

@@ -89,7 +89,7 @@ export const LandingLinksImages: React.FC<LandingLinksImagesProps> = React.memo(
                         </EuiTitle>
                         {isBeta && <BetaBadge text={betaOptions?.text} />}
                       </div>
-                      <EuiText size="s" color="text" css={styles.description}>
+                      <EuiText size="s" css={styles.description}>
                         {description}
                       </EuiText>
                     </EuiFlexItem>