build: config for new ref docs (#1202)

Author: yoshi-automation

handwritten/spanner/.kokoro/release/docs-devsite.cfg

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-spanner.git",
-        "sha": "f947b12ae74e06b26505f8ff52330bb63fcb77bd"
+        "sha": "d835ba21489885f1fc092011d955c9ca5ef162ca"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "3a00b7fea8c4c83eaff8eb207f530a2e3e8e1de3"
+        "sha": "89d431fb2975fc4e0ed24995a6e6dfc8ff4c24fa"
       }
     }
   ],