Remove saslPassword and authType (eventing)

ns_server is removing the saslPassword and authType bucket properties as they are no longer used (MB-44777). The eventing 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).

Here's a grep output...I didn't check if all of the instances of authType are applicable.

stevewatanabe @ ~/couchbase2/goproj/src/github.com/couchbase/eventing ((HEAD detached at 603928b3)) $ xg saslPassword *
dcp/pools.go: Password string `json:"saslPassword"`
stevewatanabe @ ~/couchbase2/goproj/src/github.com/couchbase/eventing ((HEAD detached at 603928b3)) $ xg authType *
dcp/pools.go: AuthType string `json:"authType"`
flatbuf/cfg_schema.fbs: authType:string;
gen/flatbuf/cfg/Curl.go:func CurlAddAuthType(builder *flatbuffers.Builder, authType flatbuffers.UOffsetT) {
gen/flatbuf/cfg/Curl.go: builder.PrependUOffsetTSlot(2, flatbuffers.UOffsetT(authType), 0)
gen/flatbuf/cfg_schema_generated.h: const flatbuffers::String *authType() const {
gen/flatbuf/cfg_schema_generated.h: verifier.VerifyString(authType()) &&
gen/flatbuf/cfg_schema_generated.h: void add_authType(flatbuffers::Offset<flatbuffers::String> authType) {
gen/flatbuf/cfg_schema_generated.h: fbb_.AddOffset(Curl::VT_AUTHTYPE, authType);
gen/flatbuf/cfg_schema_generated.h: flatbuffers::Offset<flatbuffers::String> authType = 0,
gen/flatbuf/cfg_schema_generated.h: builder_.add_authType(authType);
gen/flatbuf/cfg_schema_generated.h: const char *authType = nullptr,
gen/flatbuf/cfg_schema_generated.h: authType ? _fbb.CreateString(authType) : 0,
tests/functional_tests/basic_auth.go: authType := credentialsBase64[0]
tests/functional_tests/basic_auth.go: if authType != "Basic" {
util/util.go: authTypeEncoded := builder.CreateString(app.DeploymentConfig.Curl[i].AuthType)
util/util.go: cfg.CurlAddAuthType(builder, authTypeEncoded)