fix(theme): correct typo in Italian legend title (#128)

Author: il-santo

stdlib/C4/themes/puml-theme-C4Language_italian.puml

@@ -2,7 +2,7 @@
 
 !$BOUNDARY_LEGEND_TEXT ?= "confine"
 
-!$LEGEND_TITLE_TEXT ?= "Leggenda"
+!$LEGEND_TITLE_TEXT ?= "Legenda"
 
 !$LEGEND_BOUNDARY ?= "confine"
 !$LEGEND_BOUNDARY_PRE_PART ?= "confine del "