Fix grammar in srp_verifier.txt

CLA: trivial

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #24237)

apps/demoSRP/srp_verifier.txt

@@ -1,6 +1,6 @@
 # This is a file that will be filled by the openssl srp routine.
 # You can initialize the file with additional groups, these are
-# records starting with an I followed by the g and N values and the id.
+# records starting with an 'I' followed by the 'g' and 'N' values and the ID.
 # The exact values ... you have to dig this out from the source of srp.c
 # or srp_vfy.c
-# The last value of an I is used as the default group for new users.
+# The last value of an 'I' is used as the default group for new users.