selftests: seg6: fix instaces typo in comments

Fix a typo:
instaces -> instances

The typo has been identified using codespell, and the tool does not
report any additional issues in the selftests considered.

Signed-off-by: Andrea Mayer <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/srv6_end_next_csid_l3vpn_test.sh

···
 		dev "${DUMMY_DEVNAME}"
 
 	# all SIDs for VPNs start with a common locator. Routes and SRv6
-	# Endpoint behavior instaces are grouped together in the 'localsid'
+	# Endpoint behavior instances are grouped together in the 'localsid'
 	# table.
 	ip -netns "${nsname}" -6 rule \
 		add to "${VPN_LOCATOR_SERVICE}::/16" \

tools/testing/selftests/net/srv6_end_x_next_csid_l3vpn_test.sh

···
         set_underlay_sids_reachability "${rt}" "${rt_neighs}"
 
 	# all SIDs for VPNs start with a common locator. Routes and SRv6
-	# Endpoint behavior instaces are grouped together in the 'localsid'
+	# Endpoint behavior instances are grouped together in the 'localsid'
 	# table.
 	ip -netns "${nsname}" -6 rule \
 		add to "${VPN_LOCATOR_SERVICE}::/16" \

tools/testing/selftests/net/srv6_hencap_red_l3vpn_test.sh

···
 		dev "${VRF_DEVNAME}"
 
 	# all SIDs for VPNs start with a common locator. Routes and SRv6
-	# Endpoint behavior instaces are grouped together in the 'localsid'
+	# Endpoint behavior instances are grouped together in the 'localsid'
 	# table.
 	ip -netns "${nsname}" -6 rule \
 		add to "${VPN_LOCATOR_SERVICE}::/16" \

tools/testing/selftests/net/srv6_hl2encap_red_l2vpn_test.sh

···
 		encap seg6local action End dev "${DUMMY_DEVNAME}"
 
 	# all SIDs for VPNs start with a common locator. Routes and SRv6
-	# Endpoint behaviors instaces are grouped together in the 'localsid'
+	# Endpoint behaviors instances are grouped together in the 'localsid'
 	# table.
 	ip -netns "${nsname}" -6 rule add \
 		to "${VPN_LOCATOR_SERVICE}::/16" \