chore(java): update windows build

to install maven 3.8.1 at runtime too (related to #1202)

Tested in [java-bigquerystorage](googleapis/java-bigquerystorage@7834f4f)

Source-Author: Stephanie Wang <[email protected]>
Source-Date: Tue Sep 7 13:04:27 2021 -0400
Source-Repo: googleapis/synthtool
Source-Sha: 17ee6e5c08f2eb47029beee4776ce990e56b3925
Source-Link: googleapis/synthtool@17ee6e5

Author: yoshi-automation

.github/workflows/ci.yaml

@@ -26,6 +26,9 @@ jobs:
     runs-on: windows-latest
     steps:
     - uses: actions/checkout@v2
+    - uses: stCarolas/setup-maven@v4
+      with:
+        maven-version: 3.8.1
     - uses: actions/setup-java@v1
       with:
         java-version: 8
@@ -75,4 +78,4 @@ jobs:
     - run: java -version
     - run: .kokoro/build.sh
       env:
-        JOB_TYPE: clirr
+        JOB_TYPE: clirr

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-spanner.git",
-        "sha": "c9f504829f53bfcff6f78bbbbc447cc8f10f5940"
+        "sha": "87b77a3be3fc9cb206e147dcce818b594b2c6b4b"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ad7fd76e17bf9494a3e47ff9cf445f61564432e0"
+        "sha": "17ee6e5c08f2eb47029beee4776ce990e56b3925"
       }
     }
   ],
@@ -66,7 +66,6 @@
     ".github/workflows/auto-release.yaml",
     ".github/workflows/ci.yaml",
     ".kokoro/build.bat",
-    ".kokoro/build.sh",
     ".kokoro/coerce_logs.sh",
     ".kokoro/common.cfg",
     ".kokoro/common.sh",