tools: remove redundant type "int32" from some array length params

because they are int32 be default in the absence of an explicit type.

tools/pdbgen/pdb/drawable.pdb

@@ -1000,7 +1000,7 @@ HELP
     @outargs = (
 	{ name => 'pixel', type => 'int8array',
 	  desc => 'The pixel value',
-	  array => { name => 'num_channels', type => 'int32', no_validate => 1,
+	  array => { name => 'num_channels', no_validate => 1,
 	  	     desc => 'The number of channels for the pixel' } }
     );
 
@@ -1059,7 +1059,7 @@ HELP
 	  desc => 'The y coordinate' },
 	{ name => 'pixel', type => 'int8array',
 	  desc => 'The pixel value',
-	  array => { name => 'num_channels', type => 'int32', no_validate => 1,
+	  array => { name => 'num_channels', no_validate => 1,
 	  	     desc => 'The number of channels for the pixel' } }
     );
 

tools/pdbgen/pdb/gradients.pdb

@@ -128,7 +128,7 @@ sub gradients_sample_custom {
     @inargs = (
 	{ name  => 'positions', type  => 'floatarray',
 	  desc  => 'The list of positions to sample along the gradient',
-	  array => { name => 'num_samples', type => 'int32',
+	  array => { name => 'num_samples',
 		     desc => 'The number of samples to take' } },
 	{ name => 'reverse', type => 'boolean',
 	  desc => 'Use the reverse gradient' }