Fix: Some typos found using codespell

src/saveload/strings_sl.cpp

@@ -82,7 +82,7 @@ char *CopyFromOldName(StringID id)
 				case 0xB8: c = 0x017E; break; // z with caron
 				case 0xBC: c = 0x0152; break; // OE ligature
 				case 0xBD: c = 0x0153; break; // oe ligature
-				case 0xBE: c = 0x0178; break; // Y with diaresis
+				case 0xBE: c = 0x0178; break; // Y with diaeresis
 				default: break;
 			}