[GTK][HiDpi] Code cleanup for removal of non-cairo scale path

[deepika-u]

Currently we are using cairo for image operations we don't use non cairo scale path anymore.
Its better to remove that path now.

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

Additional context
https://bugs.eclipse.org/bugs/show_bug.cgi?id=569233#c5

@SyntevoAlex @akurtakov @merks
Please do let us know if you have any objection/suggestion for proceeding on this issue.

@sravanlakkimsetti
Please do let me know your opinion on this.

[akurtakov]

If it's truly unused code path I'm all for removing it.

[sravanlakkimsetti]

If it's truly unused code path I'm all for removing it.

Its unused now. The last platform that used this path was Ubuntu 18.04 with KDE (Kubuntu). Ubuntu 18.04 went out of support in 2023. So no need of keeping this path now.

[SyntevoAlex]

No objections from my side.