Added empty title block to KiCad 6 deeper and sub-sheet examples

- Needed for the SCH replace test.
- In KiCad 6 the title block is optional in the file.

tests/board_samples/kicad_6/deeper.kicad_sch

@@ -4,6 +4,17 @@
 
   (paper "A4")
 
+  (title_block
+    (title "")
+    (date "")
+    (rev "")
+    (company "")
+    (comment 1 "")
+    (comment 2 "")
+    (comment 3 "")
+    (comment 4 "")
+  )
+
   (lib_symbols
     (symbol "Device:R" (pin_numbers hide) (pin_names (offset 0)) (in_bom yes) (on_board yes)
       (property "Reference" "R" (id 0) (at 2.032 0 90)

tests/board_samples/kicad_6/sub-sheet.kicad_sch

@@ -4,6 +4,17 @@
 
   (paper "A4")
 
+  (title_block
+    (title "")
+    (date "")
+    (rev "")
+    (company "")
+    (comment 1 "")
+    (comment 2 "")
+    (comment 3 "")
+    (comment 4 "")
+  )
+
   (lib_symbols
     (symbol "74xx:74LS04" (in_bom yes) (on_board yes)
       (property "Reference" "U" (id 0) (at 0 1.27 0)