Show non-driven error on single-pin nets

Better to have both the single-pin error message and the non-driven
error message when an input pin is not connected than miss error
messages when the pin is connected to a blank net

Fixes https://gitlab.com/kicad/code/kicad/issues/10430

(cherry picked from commit e740db61f5)

eeschema/dialogs/dialog_erc.cpp

@@ -466,7 +466,7 @@ void DIALOG_ERC::testErc()
             || settings.IsTestEnabled( ERCE_POWERPIN_NOT_DRIVEN )
             || settings.IsTestEnabled( ERCE_PIN_NOT_DRIVEN ) )
     {
-        tester.TestPinToPin();
+         tester.TestPinToPin();
     }
 
     // Test similar labels (i;e. labels which are identical when

eeschema/erc.cpp

@@ -466,10 +466,6 @@ int ERC_TESTER::TestPinToPin()
             }
         }
 
-        // Single-pin nets are handled elsewhere
-        if( pins.size() < 2 )
-            continue;
-
         std::set<std::pair<SCH_PIN*, SCH_PIN*>> tested;
 
         SCH_PIN* needsDriver = nullptr;