ci: fix dmg transparent background bug

[siddarthkay]

Summary

Attempt to fix transparent background missing from dmg on MacOS.

Currently it looks like this :

Whereas it should have looked like this :

[status-im-auto]

Jenkins Builds

❔	Commit	#️⃣	Finished (UTC)	Duration	Platform	Result
✔️	0d0b697	#1	2025-08-23 01:50:50	~8 min	tests/nim	📄log
✔️	0d0b697	#1	2025-08-23 01:57:05	~14 min	tests/ui	📄log
❌	0d0b697	#1	2025-08-23 01:57:49	~14 min	macos/aarch64	📄log
✔️	0d0b697	#1	2025-08-23 01:59:34	~16 min	linux/x86_64	📦tgz
❌	0d0b697	#1	2025-08-23 02:02:26	~19 min	macos/aarch64-nwaku	📄log
✔️	0d0b697	#1	2025-08-23 02:05:59	~23 min	linux/x86_64-nwaku	📦tgz
✔️	0d0b697	#1	2025-08-23 02:06:52	~24 min	windows/x86_64	💿exe
✔️	0d0b697	pr18709	2025-08-23 02:10:31	~10 min	tests/e2e	📊rpt
✔️	0d95f14	#2	2025-08-23 03:54:49	~5 min	tests/nim	📄log
✔️	0d95f14	#2	2025-08-23 04:00:42	~11 min	macos/aarch64	🍎dmg
✔️	0d95f14	#2	2025-08-23 04:01:03	~12 min	tests/ui	📄log
✔️	0d95f14	#2	2025-08-23 04:01:24	~12 min	linux/x86_64	📦tgz
✔️	0d95f14	#2	2025-08-23 04:06:01	~17 min	macos/aarch64-nwaku	🍎dmg
✔️	0d95f14	#2	2025-08-23 04:08:35	~19 min	linux/x86_64-nwaku	📦tgz
✔️	0d95f14	#2	2025-08-23 04:09:15	~20 min	windows/x86_64	💿exe
✔️	0d95f14	pr18709	2025-08-23 04:12:12	~10 min	tests/e2e	📊rpt