Fix misspellings and enable misspell on ci (#16285)

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

store/storetest/group_store.go

@@ -749,7 +749,7 @@ func testGroupGetMemberUsersInTeam(t *testing.T, ss store.Store) {
 	require.Nil(t, err)
 
 	// returns no members when team does not exist
-	groupMembers, err := ss.Group().GetMemberUsersInTeam(group.Id, "non-existant-channel-id")
+	groupMembers, err := ss.Group().GetMemberUsersInTeam(group.Id, "non-existent-channel-id")
 	require.Nil(t, err)
 	require.Equal(t, 0, len(groupMembers))
 
@@ -845,7 +845,7 @@ func testGroupGetMemberUsersNotInChannel(t *testing.T, ss store.Store) {
 	require.Nil(t, nErr)
 
 	// returns no members when channel does not exist
-	groupMembers, err := ss.Group().GetMemberUsersNotInChannel(group.Id, "non-existant-channel-id")
+	groupMembers, err := ss.Group().GetMemberUsersNotInChannel(group.Id, "non-existent-channel-id")
 	require.Nil(t, err)
 	require.Equal(t, 0, len(groupMembers))