chore(ci): fix typo in restrict presubmit samples ITs to only snapshot (

#554)

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Source-Link: googleapis/synthtool@f68649c

.kokoro/build.sh

@@ -78,7 +78,7 @@ samples)
 
     if [[ -f ${SAMPLES_DIR}/pom.xml ]]
     then
-        pushd {SAMPLES_DIR}
+        pushd ${SAMPLES_DIR}
         mvn -B \
           -Penable-samples \
           -DtrimStackTrace=false \

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-spanner.git",
-        "sha": "5322c951ffaac38bc89c93ab510f312412fe2c53"
+        "sha": "d92b7c21b8751d4f3aae2e8847fa6cb5d3ebd40a"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "5f6ef0ec5501d33c4667885b37a7685a30d41a76"
+        "sha": "f68649c5f26bcff6817c6d21e90dac0fc71fef8e"
       }
     }
   ],