chore(deps): update dependency google-api-core to v1.26.0 (#941)

Co-authored-by: Jeffrey Rennie <rennie@google.com>
Co-authored-by: Elliotte Rusty Harold <elharo@users.noreply.github.com>

requirements.txt

@@ -12,7 +12,7 @@ watchdog
 # temporarily install google-api-core for gapic-generator-python
 # Bazel should install this, but there is currently a bug
 # that causes the package to be skipped
-google-api-core==1.25.1
+google-api-core==1.26.0
 
 # some java processing requires xml handling
 lxml