build(deps): bump setuptools from 70.2.0 to 78.1.1 in /.kokoro

Bumps [setuptools](https://github.com/pypa/setuptools) from 70.2.0 to 78.1.1.
- [Release notes](https://github.com/pypa/setuptools/releases)
- [Changelog](https://github.com/pypa/setuptools/blob/main/NEWS.rst)
- [Commits](pypa/setuptools@v70.2.0...v78.1.1)

---
updated-dependencies:
- dependency-name: setuptools
  dependency-version: 78.1.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.kokoro/requirements.txt

@@ -531,7 +531,7 @@ zipp==3.19.2 \
     # via importlib-metadata
 
 # The following packages are considered to be unsafe in a requirements file:
-setuptools==70.2.0 \
-    --hash=sha256:b8b8060bb426838fbe942479c90296ce976249451118ef566a5a0b7d8b78fb05 \
-    --hash=sha256:bd63e505105011b25c3c11f753f7e3b8465ea739efddaccef8f0efac2137bac1
+setuptools==78.1.1 \
+    --hash=sha256:c3a9c4211ff4c309edb8b8c4f1cbfa7ae324c4ba9f91ff254e3d305b9fd54561 \
+    --hash=sha256:fcc17fd9cd898242f6b4adfaca46137a9edef687f43e6f78469692a5e70d851d
     # via -r requirements.in