chore: Release fix (#2187)

Currently the release pipeline is failing. Yesterday the release PR got mergehttps://togithub.com/googleapis/nodejs-spanner/pull/2180 but it did not trigger the publish release. 

As per offline discussion with @sofisl , this should fix the issue temporarily.

Author: surbhigarg92

handwritten/spanner/.github/release-trigger.yml

@@ -1 +1,2 @@
 enabled: true
+multiScmName: nodejs-spanner

handwritten/spanner/owlbot.py

@@ -64,7 +64,7 @@
 
 common_templates = gcp.CommonTemplates()
 templates = common_templates.node_library(source_location='build/src')
-s.copy(templates, excludes=[".kokoro/samples-test.sh"])
+s.copy(templates, excludes=[".kokoro/samples-test.sh",".github/release-trigger.yml"])
 
 node.postprocess_gapic_library_hermetic()