Fix lowercase start of a sentence

index.bs

@@ -5793,7 +5793,7 @@ At this time, one [=credential property=] is defined: the [=resident key credent
             is a Boolean value indicating whether the {{PublicKeyCredential}} returned as a result of a [=registration ceremony=]
             is a [=client-side discoverable credential=].
             If {{rk}} is [TRUE], the credential is a [=discoverable credential=].
-            if {{rk}} is [FALSE], the credential is a [=server-side credential=].
+            If {{rk}} is [FALSE], the credential is a [=server-side credential=].
             If {{rk}} is not present, it is not known whether the credential is a [=discoverable credential=] or a [=server-side credential=].
 
             Note: some [=authenticators=] create [=discoverable credentials=] even when not requested by the [=client platform=]. Because of this, [=client platforms=] may be forced to omit the {{rk}} property because they lack the assurance to be able to set it to [FALSE]. [=[RPS]=] should assume that, if the `credProps` extension is supported, then [=client platforms=] will endeavour to populate the {{rk}} property. Therefore a missing {{rk}} indicates that the created credential is most likely a [=non-discoverable credential=].