update groovyscript docs for GTCEu 2.7+

[Nrmot]

just found out that the examples in https://groovyscript-docs.readthedocs.io/en/latest/groovyscript/mods/gtceu/material/ are outdated and it should be updated.

this is just one example and there may be more outdated groovyscript docs.

as of GTCEu 2.7.4, the following example script will no longer work

import gregtech.api.GregTechAPI.MaterialEvent
import gregtech.api.unification.material.Material

event_manager.listen { MaterialEvent event ->
    def specialSteel = new Material.Builder(32002, "special_steel") // name
            .fluid("gas", false) // gas without block
            .ingot() // has ingot (and therefore dust)
            .color(0x0000FF) // pure blue
            .toolStats(10, 3, 256, 21) // tool stats
            .blastTemp(2900) // EBF temperature
            .ore() // has ore blocks
            .addOreByproducts(material('gold'), material('copper')) // add byproducts
            .cableProperties(128, 2, 4, false) // add cables
            .build() // build the actual material
}

update to this:

- new Material.Builder(32002, "special_steel"). 
+ new Material.Builder(32000, resource("modpack_modid", "special_steel"))

There are more outdated examples and feel free to list them in here.

[Rongmario]

Feel free to PR straight into the repository

[brachy84]

done https://github.com/CleanroomMC/cleanroom-website/pull/9