Exported var/type/method missing comment

[arvindbr8]

Found a couple of linter issues from the patch set in #6915 during our weekly import

1. missing comment on the following exported type/method

grpc-go/xds/internal/xdsclient/xdsresource/filter_chain.go

Line 508 in d66bc9b

func (fcm *FilterChainManager) FilterChains() []*FilterChain {

grpc-go/xds/internal/xdsclient/xdsresource/filter_chain.go

Line 100 in d66bc9b

type UsableRouteConfiguration struct {

2. There is a typo in the comment s/TriggerXDSResourceNotFoundClient/TriggerXDSResourceNameNotFoundClient/

grpc-go/internal/internal.go

Line 193 in d66bc9b

// TriggerXDSResourceNotFoundClient invokes the testing xDS Client singleton