Fix Git error during project configuration

[YoshiWalsh]

Previously project configuration would fail with "fatal: couldn't find remote ref d541301" (git v2.55.0)

This affected almost all platformio commands too. E.g.

 *  Executing task: platformio run --environment RAK_3401_repeater 

Processing RAK_3401_repeater (board: rak3401; platform: nordicnrf52; framework: arduino)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Tool Manager: Installing git+https://github.com/meshcore-dev/Adafruit_nRF52_Arduino#d541301
git version 2.55.0
hint: Using 'master' as the name for the initial branch. This default branch name
hint: will change to "main" in Git 3.0. To configure the initial branch name
hint: to use in all of your new repositories, which will suppress this warning,
hint: call:
hint:
hint:   git config --global init.defaultBranch <name>
hint:
hint: Names commonly chosen instead of 'master' are 'main', 'trunk' and
hint: 'development'. The just-created branch can be renamed via this command:
hint:
hint:   git branch -m <name>
hint:
hint: Disable this message with "git config set advice.defaultBranchName false"
Initialized empty Git repository in /root/.platformio/.cache/tmp/pkg-installing-wokqua5c/.git/
fatal: couldn't find remote ref d541301
VCSBaseException: VCS: Could not process command ['git', 'fetch', '--depth=1', 'origin', 'd541301']

Per https://git-scm.com/docs/git-fetch#Documentation/git-fetch.txt-refspec, the argument needs to be either a ref (read: branch or tag) or a "fully spelled hex object name". The error appears to have been caused by the partial hex.

This requirement is also mentioned in this SO answer: https://stackoverflow.com/a/30701724

After this change, project configuration now succeeds.