It's not required
The rules on concentration can be found on page 203 of Player's Handbook. Concentration is only specified to end in these four ways:
- Ending concentration voluntarily
- Casting another spell that requires concentration, including spells with a longer casting time than a single action or reaction (per page 202) or maintaining a readied spell (per page 193)
- Taking damage and failing the saving throw to maintain concentration
- Becoming incapacitated or killed
There is no mention of one having to maintain any of the components, including the material ones, of the spell to maintain concentration.
Item descriptions are found on page 151. Under Holy Symbol, it is simply stated that the item can be used as a spellcasting focus, without special rules regarding concentration.