Add clarity around variables used with scheduled triggers

[MarcL]

Add some clarity around how variables don't work as expected with scheduled triggers:

• Update scheduled trigger page to include a warning around using variables in cron expressions
• Update scheduled triggers common issues page to include details of variables not working as expected

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[github-actions]

Overall readability score: 44.9 (🔴 -0.01)

File	Readability
common-issues.md	67.6 (🔴 -3.94)
index.md	84.85 (🔴 -4.25)

View detailed metrics

🟢 - Shows an increase in readability
🔴 - Shows a decrease in readability

File	Readability	FRE	GF	ARI	CLI	DCRS
common-issues.md	67.6	56.35	9.15	9.5	10.2	7.63
	🔴 -3.94	🔴 -9.58	🔴 -0.72	🔴 -0.6	🔴 -0.06	🔴 -0.05
index.md	84.85	67.76	6.57	7.6	8.8	5.7
	🔴 -4.25	🔴 -9.27	🔴 -0.51	🔴 -0.5	🔴 -0.47	🔴 -0.14

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	44.9	35.72	11.36	14.57	14.19	8.41
	🔴 -0.01	🔴 -0.01	🟢 +0	🟢 +0	🟢 +0	🟢 +0

View metric targets

Metric	Range	Ideal score
Flesch Reading Ease	100 (very easy read) to 0 (extremely difficult read)	60
Gunning Fog	6 (very easy read) to 17 (extremely difficult read)	8 or less
Auto. Read. Index	6 (very easy read) to 14 (extremely difficult read)	8 or less
Coleman Liau Index	6 (very easy read) to 17 (extremely difficult read)	8 or less
Dale-Chall Readability	4.9 (very easy read) to 9.9 (extremely difficult read)	6.9 or less

[evilnick]

@MarcL Many thanks for your efforts here - I'm going to add some comments/suggestions as I see there have been some questions and issues related to this and it would be good to clear them all up at once.

[evilnick]

Thanks again @MarcL. Just a few comments to hopefully make this even more useful!

[evilnick]

Some of the queries I have seen have been along the lines of "If i have a schedule of 1 hour and I edit the workflow and save it, does the one hour reset to from the time I saved it?" It would be good if we could answer that here too!

[MarcL]

@evilnick - Do you mean that I should add this as a separate point? It's not related to variables right?