fix: server/predictors/chemprop/requirements.txt to reduce vulnerabil…

…ities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-TENSORFLOW-1315149

server/predictors/chemprop/requirements.txt

@@ -9,7 +9,7 @@ pandas-flavor>=0.2.0
 scikit-learn>=0.22.2.post1
 scipy==1.4.1
 tensorboardX>=2.0
-tensorflow>=1.13.1
+tensorflow>=2.12.0rc1
 torch>=1.5.1
 tqdm>=4.45.0
 typed-argument-parser>=1.5.2