chore(ci): fix typo in restrict presubmit samples ITs to only snapshot (#554)

This PR was generated using Autosynth. 🌈 Synth log will be available here: https://source.cloud.google.com/results/invocations/fe68bcb3-d907-42e1-b991-ed69a91c3c34/targets - [x] To automatically regenerate this PR, check this box. Source-Link: googleapis/synthtool@f68649c

Author: yoshi-automation

.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"
  }
  }
  ],