Remove saslPassword and authType (goxdcr)

ns_server is removing the saslPassword and authType bucket properties as they are no longer used (MB-44777). The XDCR component has a least one file which uses or references them. Please remove the code taking into account that mixed version clusters must be supported (may or may not be an issue for this component).

stevewatanabe @ ~/couchbase2/goproj/src/github.com/couchbase/goxdcr ((HEAD detached at 3645f8b)) $ grep -RiIl saslPassword *
base/filter/testInternalData/pools_default_buckets_b2.json
base/filter/testInternalData/pools_default_buckets.json
base/constant.go
factory/xdcr_factory.go
utils/testK8ExternalData/pools_default_buckets_default.json
utils/testK8ExternalData/pools_default_buckets.json
utils/testInternalData/pools_default_buckets_b2.json
utils/testInternalData/pools_default_buckets.json
utils/utils.go
utils/testExternalData/pools_default_buckets_b2.json
utils/testExternalData/targetBucketInfo_alt.json
utils/testExternalData/pools_default_buckets.json

stevewatanabe @ ~/couchbase2/goproj/src/github.com/couchbase/goxdcr ((HEAD detached at 3645f8b)) $ grep -RiIl authType *
base/filter/testInternalData/pools_default_buckets_b2.json
base/filter/testInternalData/pools_default_buckets.json
base/constant.go
utils/testK8ExternalData/pools_default_buckets_default.json
utils/testK8ExternalData/pools_default_buckets.json
utils/testInternalData/pools_default_buckets_b2.json
utils/testInternalData/pools_default_buckets.json
utils/utils.go
utils/testExternalData/pools_default_buckets_b2.json
utils/testExternalData/targetBucketInfo_alt.json
utils/testExternalData/pools_default_buckets.json