docs(va): in-report screenshots for the mapping and the banner

Both images on the embed page were still captured from a local sandbox with the
editor as the top-level document, so neither showed the report around it.

- va-parmap-filtered.png: the report viewer, prompt DROPDOWN_TAB1 (relabelled on
  the report, not matching any column) and SOME_DATE, with
  FILTER : ( ( SOME_DROPDOWN = 'Option 1' AND SOME_DATE = '01JUL1960'd ) ) over
  21 rows - the mapped parameter filtering a column that is not its name
- va-parmap-banner.png: the same object with a malformed entry
  (va_parmap=SOME_DATE, no hyphen), showing the warning banner over a populated,
  filtered grid

The caption for the mapping now says the date parameter beside it is
name-matched, which is what the picture shows.

va-parmap-transform.png is removed rather than replaced: the deployment used for
these captures predates the ADD/RANGE work, so there is no honest in-report
picture of a date anchor to take, and a sandbox capture would be the one image on
the page without the report around it. The section keeps the syntax, the anchors
and the examples table.

docs/visual-analytics.md

@@ -73,7 +73,7 @@ Repeat the parameter to add mappings.  A report with two tabs, each holding its
 | Tab 1 | `...?embed=va&va_parmap=REGION_TAB1-REGION` |
 | Tab 2 | `...?embed=va&va_parmap=REGION_TAB2-REGION` |
 
-The applied filter is visible in the editor, above the grid - here the parameter `DROPDOWN_TAB1` filtering `SOME_DROPDOWN`, which is not its name:
+The applied filter is visible in the editor, above the grid - here the parameter `DROPDOWN_TAB1` filtering `SOME_DROPDOWN`, which is not its name (the date parameter beside it is name-matched, which is the default):
 
 ![A va_parmap mapping filtering a column](img/va-parmap-filtered.png)
 
@@ -120,11 +120,7 @@ A mapping can resolve the parameter value through a **named date anchor** before
 https://yourserver/DC/#/editor/<library>/<table>?embed=va&va_parmap=SELECTED_DATE-D_DATE:ADD(QUARTER_START,-1)
 ```
 
-A report that sends `SELECTED_DATE = 27FEB1961` then filters `D_DATE` on 1961-02-27 **and** 1960-10-01 - the selected date, plus the same point one quarter earlier:
-
-In the screenshot below the mapping is `SELECTED_DATE-SOME_DATE:ADD(QUARTER_START,-1)` against the demo table, and the parameter sends 27FEB1961:
-
-![A date anchor applied to the filter](img/va-parmap-transform.png)
+A report that sends `SELECTED_DATE = 27FEB1961` then filters `D_DATE` on 1961-02-27 **and** 1960-10-01 - the selected date, plus the same point one quarter earlier.
 
 The clause carries both values, so the row for the selected date and the row for the previous quarter are both included.