Update labels, links and descriptions renaming power-to-gas to electrolysis

[robindesmit-quintel]

Context

The labelling of electrolysis is not consistent in the model and should be revised.

Implemented changes

• Updated descriptions by renaming power-to-gas to electrolysis.
• Updated the title of section "Power-to-gas" located under Flexibility>Electricity > Electricity conversion> Description of Technologies
• Updated the link to renamed section. This link is located in Hydrogen production.
• Note: power-to-gas is not renamed in Overview of costs per sector > Storage and conversion.

Related

Closes issue: quintel/etsource#3086

Goes with pull requests: quintel/etmodel#4707

Checklist

• I have tested these changes
• I have updated documentation as needed
• I have tagged the relevant people for review

[kndehaan]

Looking good! I implemented some minor improvements.

There are still some files that refer to power to gas. Could you correct it in these files:

• cost-dashboard.md
• cost-methods.md
• cost-overview-per-sector.md
• interface.md