release-24.1: pkg/ui: properly derive XScale in statement details page

[abarganier]

Backport 1/1 commits from #121366.

/cc @cockroachdb/release

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Fixes: #121362

Epic: none

#118680 introduced code to align the timeseries charts on the statement details page to the time range set by the time picker, instead of the time range that we had available data for.

The code contained a bug where it would set the start & end of the XScale to Moment.prototype.valueOf instead of the result of calling Moment.prototype.valueOf(). This causes the start & end timestamps to be set to functions, instead of unix timestamps, which broke the charts.

This PR simply invokes the function.

Release note (bug fix): The timeseries graphs shown on the SQL Activity statement details page in DB Console will now render properly, after fixing a bug related to setting the time range of the charts.

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Release justification: fix for a UI bug found in the SQL Activity statement details page.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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  here).
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
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Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[dhartunian]

Confirmed with @abarganier that this fix was manually verified.

[abarganier]

TFTRs!