Update getPullRequestsMergedBetween to run pre-set string command

[Jag96]

@roryabraham will you please review this
cc @AndrewGable

Details

This PR attempts to fix an issue where when a CP happens, the toRef is set to an empty string, even though it is being logged out properly beforehand. Came up with this approach after looking at this SO and seeing that our other usages of execSync only set variables that are separated by spaces, so perhaps there is an issue in this case. I also added a log line that will spit out the command to ensure that the string is what we expect it to be.

Fixed Issues

Related to https://github.com/Expensify/Expensify/issues/168349, possibly a fix 🤞

Tests

1. Merge this PR
2. With a staging deploy checklist open, CP a new PR
3. Confirm that the deploy checklist issue description isn't updated with PRs that aren't on staging

I ran tests locally to confirm that the function still works as expected:

QA Steps

None

Screenshots

N/A

[aldo-expensify]

@Jag96 from what I see, and I think this what you wanted to achieve, this is logging some extra stuff and not changing the return of the function. But unfortunately due to my lack of experience in the area, I don't know how to test this! Feel free to remove me and find someone else that can give you a better input about this if you need :)

[roryabraham]

Definitely worth a shot! Let's test this on the next checklist by CPing it as soon as the checklist is locked.

[OSBotify]

⚠️ ⚠️ Heads up! This pull request has the CP Staging label. ⚠️ ⚠️
Merging it will cause it to be immediately deployed to staging, even if the open StagingDeployCash deploy checklist is locked.

[roryabraham]

cc @isagoico because I know you'll be more stoked about this than anyone if it works.

[aldo-expensify]

I ran the test local test and confirmed that it is working. I'll let the merge to you guys because I'm not familiarized enough with the process to test it in staging.

[Jag96]

For context, we're holding off on merging this until we have a fresh checklist to confirm the issue is fixed. Putting this on HOLD for now

[Jag96]

Going to CP this to Staging before the prod deploy

[OSBotify]

🚀 Deployed to production in version: 1.0.82-7🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

[OSBotify]

🚀 Deployed to staging in version: 1.0.82-7🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

[OSBotify]

🚀 Deployed to staging in version: 1.0.82-8🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

[OSBotify]

🚀 Deployed to production by @francoisl in version: 1.0.83-1 🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	failure ❌
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅