chore: remove obsolete replacements from synth.py (#211)

```
2020-03-05 14:36:59,366 synthtool > No replacements made in **/doc/google/protobuf/doc_timestamp.js for pattern https:\/\/cloud\.google\.com[\s\*]*http:\/\/(.*)[\s\*]*\), maybe replacement is no longer needed?
2020-03-05 14:36:59,378 synthtool > No replacements made in **/doc/google/protobuf/doc_timestamp.js for pattern toISOString\], maybe replacement is no longer needed?
```

packages/google-cloud-scheduler/synth.py

@@ -40,16 +40,6 @@
 templates = common_templates.node_library(source_location='build/src')
 s.copy(templates)
 
-# [START fix-dead-link]
-s.replace('**/doc/google/protobuf/doc_timestamp.js',
-        'https:\/\/cloud\.google\.com[\s\*]*http:\/\/(.*)[\s\*]*\)',
-        r"https://\1)")
-
-s.replace('**/doc/google/protobuf/doc_timestamp.js',
-        'toISOString\]',
-        'toISOString)')
-# [END fix-dead-link]
-
 # Node.js specific cleanup
 subprocess.run(['npm', 'install'])
 subprocess.run(['npm', 'run', 'fix'])