Fix MathCAT with MultiLang add-on" (#19920)
Fixes #19784
### Summary of the issue:
When using the [MultiLang speech synth
driver](https://blindhelp.net/software/multilang) with MathCAT's
relative speech rate at anything other than 1x, math will fail to read.
### Description of user facing changes:
Math can once again be read with this add-on if the relative rate is not
100%. Note that the relative rate will have no effect, since `MultiLang`
does not support the `RateCommand`.
### Description of developer facing changes:
None
### Description of development approach:
Rather than simply popping from `resetProsody` once in
`mathPres.MathCAT.speech.convertSSMLTextForNVDA`, pop from it while it
is not empty. This means that we:
* Will reset all prosody parameters in the reverse order to which they
were set; and
* We won't try and pop from an empty list (which was the cause of this
bug).
### Testing strategy:
With math relative speech rate set to 50%:
1. Reproduced the issue by launching a version of NVDA without this
patch.
2. Read some MathML.
3. In the python console, executed `from speech.speech import
getSynth;getSynth().supportedCommands.clear()`.
4. Attempted to read the same math.
5. Confirmed the fix by running the patched version from source, and
repeating steps 2 through 4 inclusive with no issue.
### Known issues with pull request:
None
