Update hugo build timeout

According to https://gohugo.io/getting-started/configuration/#timeout,
the timeout value should be a duration (e.g. `100s`) or number of
milliseconds. Current value of 30000 translates to 30 seconds.

This PR updates the timeout in hope it resolves the netlify preview
issues that show up frequently during past weeks.

config.toml

@@ -15,7 +15,7 @@ disableKinds = ["taxonomy", "taxonomyTerm"]
 
 ignoreFiles = [ "(?:^|/)OWNERS$", "README[-]+[a-z]*\\.md", "^node_modules$", "content/en/docs/doc-contributor-tools" ]
 
-timeout = 3000
+timeout = "180s"
 
 # Highlighting config.
 pygmentsCodeFences = true