manuals: fix typos in zpool-upgrade man page

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Signed-off-by: nav1s <[email protected]>
Closes #17797

Author: nav1s

man/man8/zpool-upgrade.8

@@ -65,10 +65,10 @@ property).
 .Cm upgrade
 .Fl v
 .Xc
-Displays legacy ZFS versions supported by the this version of ZFS.
+Displays legacy ZFS versions supported by this version of ZFS.
 See
 .Xr zpool-features 7
-for a description of feature flags features supported by this version of ZFS.
+for a description of features supported by this version of ZFS.
 .It Xo
 .Nm zpool
 .Cm upgrade