fix: Heartbeat demo should not print the interrupt message when stopped

[rboni-dk]

No description provided.

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
dk-installer.py	1131	273	76%	93–94, 106–118, 138–139, 188, 228–235, 242, 254, 276–277, 319, 369–372, 391–392, 394, 444–473, 477–510, 541–550, 609, 745, 776–781, 855–856, 866, 882–886, 889, 892, 895, 906–939, 1065–1076, 1125–1140, 1143–1154, 1171–1172, 1209–1210, 1236–1237, 1244, 1249, 1255–1256, 1289–1292, 1301–1302, 1307–1308, 1324–1335, 1380–1382, 1561–1586, 1624–1627, 1696–1699, 1724, 1749–1751, 1801, 1803, 1805, 1914–1915, 1943, 1992–2031, 2071–2078, 2094–2102, 2172–2197, 2204–2213, 2222–2275, 2279–2314, 2318–2336
TOTAL	1131	273	76%

Tests	Skipped	Failures	Errors	Time
94	0 💤	0 ❌	0 🔥	1.165s ⏱️