Update dependency google-api-core to v1.18.0 (#441)

Co-authored-by: Dov Shlachter <dovs@google.com>

Author: renovate-bot

packages/gapic-generator/requirements.txt

@@ -1,5 +1,5 @@
 click==7.1.2
-google-api-core==1.17.0
+google-api-core==1.18.0
 googleapis-common-protos==1.52.0
 jinja2==2.11.2
 MarkupSafe==1.1.1