squashfs-tools: enable zstd compression by default

Requested via:
  https://github.com/openwrt/packages/issues/19111

PKG_RELEASE is set to AUTORELEASE, so no need to bump.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
(cherry picked from commit f0d45ba340)

utils/squashfs-tools/Config.in

@@ -20,4 +20,4 @@ config SQUASHFS_TOOLS_ZSTD_SUPPORT
 	depends on PACKAGE_squashfs-tools-mksquashfs || PACKAGE_squashfs-tools-unsquashfs
 	bool "Enable ZSTD support"
 	select PACKAGE_libzstd
-	default n
+	default y