Remove unnecessary backslash from regex patterns

[mvandenburgh]

Related: dandi/dandi-archive#2179

VJSF 3 does not work with the current schema due to these regex patterns being flagged by ajv as invalid -
https://github.com/dandi/dandi-schema/blob/master/dandischema/models.py#L1615
https://github.com/dandi/dandi-schema/blob/master/dandischema/models.py#L969

In particular, the \ character before the colons is triggering it. I confirmed that removing it fixes the issue, and VJSF renders the schema correctly. VJSF 3 offloads a significant amount of the validation/schema parsing to ajv compared to VJSF 2, so I believe that is why this is just coming up now.

@yarikoptic @candleindark @satra what is the purpose of the backslash here? From my understanding, the : character shouldn't need to be escaped in a regex. And if there's no particular reason for it to exist, can we remove it?

[satra]

And if there's no particular reason for it to exist, can we remove it?

sure.

[yarikoptic]

I also do not see a point of having them... there is no specific commit which added them , so most likely some "historical artifact". submitting PR