Clean up install & update shell scripts

[roens]

Clean up install & update shell scripts

Fixed quoting of the FILENAME variable to work when the path of the passed argument contains a space. Also fixed syntactical issues called out by shellcheck in multi-condition if statements. This has been an issue for (at least) me for every install or update I've attempted, as I do not unnecessarily cd into the dir containing the downloaded release files. It's also good practice to quote variables to keep the shell from "globbing and word splitting" the value of the variable.

Also normalized indentation chars (was mix of tabs & spaces) and trailing whitespace.

In the attestations below, I've marked the nrf52840-based devices as "n/a" as these shell scripts are not used for updating them.

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • LilyGo T-Deck
  • LilyGo T-Beam
  • RAK WisBlock 4631 n/a
  • Seeed Studio T-1000E tracker card n/a
  • Other (please specify below) n/a

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[fifieldt]

Thanks for your attention to detail!

Let's see if trunk is happy with the whitespace changes :D