TB: Fix errors found by schema validator

- Passing () as the side to the unit util macros results in an empty side key
  There's no reason not to just pass 1 instead though.
- [modify_side] does not support [filter]; instead it uses [filter_side]
  However, it also supports inline side which is sufficient here,
  so just use that instead.

This covers both difficulty levels; TB is now clean of schema issues.

data/campaigns/Two_Brothers/scenarios/01_Rooting_Out_a_Mage.cfg

@@ -143,17 +143,17 @@ Will he heed the call? I do not know if he has kept the amulet; we have not spok
         )}
 
         # The armed villagers, beware them
-        {NAMED_LOYAL_UNIT () Spearman 30 22 Alwyn  (_ "Alwyn")}  {FACING nw}
-        {NAMED_LOYAL_UNIT () Spearman 30 21 Brent  (_ "Brent")}  {FACING nw}
-        {NAMED_LOYAL_UNIT () Spearman 31 22 Cadell (_ "Cadell")} {FACING nw}
-        {NAMED_LOYAL_UNIT () Spearman 32 19 Dannen (_ "Dannen")} {FACING nw}
-        {NAMED_LOYAL_UNIT () Bowman   33 19 Efran  (_ "Efran")}  {FACING nw}
-        {NAMED_LOYAL_UNIT () Footpad  32 18 Faren  (_ "Faren")}  {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Spearman 30 22 Alwyn  (_ "Alwyn")}  {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Spearman 30 21 Brent  (_ "Brent")}  {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Spearman 31 22 Cadell (_ "Cadell")} {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Spearman 32 19 Dannen (_ "Dannen")} {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Bowman   33 19 Efran  (_ "Efran")}  {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Footpad  32 18 Faren  (_ "Faren")}  {FACING nw}
 
         # Arvith’s mercenary band
-        {NAMED_LOYAL_UNIT () Horseman 33 21 Tarek  (_ "Tarek")}  {FACING nw}
-        {NAMED_LOYAL_UNIT () Horseman 32 21 Hann   (_ "Hann")}   {FACING nw}
-        {NAMED_LOYAL_UNIT () Horseman 33 20 Magrid (_ "Magrid")} {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Horseman 33 21 Tarek  (_ "Tarek")}  {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Horseman 32 21 Hann   (_ "Hann")}   {FACING nw}
+        {NAMED_LOYAL_UNIT 1 Horseman 33 20 Magrid (_ "Magrid")} {FACING nw}
 
         [objectives]
             side=1