update text for the Tax Number component (#54)

Co-authored-by: Patrick Wang <root@NI502169.idir.BCGOV>

btr-web/btr-main-app/lang/en.json

@@ -10,7 +10,7 @@
   },
   "texts": {
     "citizenshipPermanentResidency": "Indicate if this person is a citizen or permanent resident of Canada, or list all of the non-Canadian citizenship(s) of this person. If this person is a Citizen or Permanent resident of Canada, listing of multiple citizenships is not required.",
-    "taxNumber": "A Social Insurance Number (SIN), an Individual Tax Number (ITN), or a Temporary Taxation Number (TTN) is required if this person has one.",
+    "taxNumber": "A 9-digit Social Insurance Number (SIN), an Individual Tax Number (ITN), or a Temporary Taxation Number (TTN) is required if this person has one.",
     "taxResidency": "Indicate if this person is a resident of Canada for Income Tax purposes."
   },
   "placeholders": {