build: only check --engine-strict for production deps (#490)

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Source-Link: googleapis/synthtool@5451633

packages/google-cloud-monitoring/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-monitoring.git",
-        "sha": "7857c6c3420dfb0040e2bd43fcb8440c34b0f255"
+        "sha": "c9b8be7896efbb5a12cc4d392a4f9fcbb287d7a9"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0c868d49b8e05bc1f299bc773df9eb4ef9ed96e9"
+        "sha": "5451633881133e5573cc271a18e73b18caca8b1b"
       }
     }
   ],