docs(filter): the applied clause carries SAS temporal literals

The clause shown above the grid is the resolved WHERE clause, so a date,
datetime or time filter reads as a SAS literal rather than the internal day or
second count.  Note it on the filter page and on the MPE_FILTERSOURCE RAW_VALUE
column, which is where the value is stored.

docs/tables/mpe_filtersource.md

@@ -17,5 +17,5 @@ The `MPE_FILTERSOURCE` table stores the individual query lines of each filter cr
  - `SUBGROUP_ID num`: Identifier of the subgroup to which this line belongs
  - `VARIABLE_NM char(32)`: The variable being filtered
  - `OPERATOR_NM char(12)`: The filter operator (e.g. `=`, `>`, `IN`)
- - `RAW_VALUE char(4000)`: The filter value
+ - `RAW_VALUE char(4000)`: The filter value. A date, datetime or time is stored as a SAS literal (for example `'20APR2042'd`, `'01JAN1960:00:00:42'dt`, `'00:00:42't`), so the clause shown above the grid reads as a date rather than the internal day or second count.
  - `PROCESSED_DTTM num`: Datetime the filter line was created