Update deprecated syntax for future rstan compatibility

[andrjohns]

Now that rstan 2.26 is available on CRAN we need to update the deprecated syntax in your package's Stan models, otherwise it will fail to install with an upcoming version of RStan.

The following updates have been made:

• New array syntax

More information about the deprecated and removed syntax in Stan can be found here:

• https://mc-stan.org/docs/functions-reference/deprecated-functions.html
• https://mc-stan.org/docs/functions-reference/removed-functions.html

If you could merge and submit to CRAN soon, it would be greatly appreciated.

Let me know if you have any questions about these changes.

Thanks!

[codecov[bot]]

Codecov Report

Patch coverage is 100.00% of modified lines.

Files Changed	Coverage
R/stan-dina.R	100.00%
R/stan-gqs.R	100.00%
R/stan-lcdm.R	100.00%
R/stan-strc.R	100.00%
R/utils-extract.R	100.00%
R/utils.R	100.00%

:loudspeaker: Thoughts on this report? Let us know!.

[andrjohns]

@wjakethompson would it be possible to push these changes to CRAN soon? Otherwise your package will break with the next rstan version

[wjakethompson]

@wjakethompson would it be possible to push these changes to CRAN soon? Otherwise your package will break with the next rstan version

@andrjohns Yes-- will plan on submitting to CRAN later this week. Thanks!

[wjakethompson]

@andrjohns This has made its way to CRAN.