Update generic PETG 1.75mm temperatures

[louisrousseau]

The included 1.75mm temperature values are much lower than those recommended on the different PETG filament boxes I have on hand.

Took values from the 2.85mm generic in generic_petg.xml.fdm_material which were last updated in PR #161 two years ago and also fit within what's on the aforementioned boxes.

[louisrousseau]

@wawanbreton any chance this PR gets merged?

[wawanbreton]

Hi @louisrousseau,
This is quite a big change because it impacts a generic material. I will discuss that with our material experts team.

[wawanbreton]

So we had a conversation about this change, and this is the conclusion:

• We do agree that the default temperature is too low, and we would like to merge this PR
• However, there are currently profiles that rely on those temperatures, and some of them actually "fix" the too low temperature. Those profiles would become unusable if we only change the base temperature. Here is an example of such a profile: https://github.com/Ultimaker/Cura/blob/main/resources/quality/atmat_signal_pro/signal_pro_v6_0.40_PETG_fine.inst.cfg

So if possible, could you make an associated PR on the Cura repository, with the following changes:

• Identify and fix all the profiles that actually change one of the concerned temperatures
• Do not change the profiles that use the base temperatures, they will take advantage of this change