Revert "chore(deps): update dependency protobuf to v3.20.2" (#1674)

Revert "chore(deps): update dependency protobuf to v3.20.2 (#1659)"

This reverts commit b59cf7b5a91ecab29e21fdfbb7e3b81066229be4.
Source-Link: googleapis/synthtool@a66e346
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-java:latest@sha256:bd316b9a591c45264775ecaba72e37d65905925c323b68e51a08c4126e4b6d0a

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,4 +13,4 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-java:latest
-  digest: sha256:ae72564aa9c368b9ccd96f4af21f87889fd83b9e60635b80844deb5a2ccd08aa
+  digest: sha256:bd316b9a591c45264775ecaba72e37d65905925c323b68e51a08c4126e4b6d0a

README.md

@@ -56,13 +56,13 @@ implementation 'com.google.cloud:google-cloud-spanner'
 If you are using Gradle without BOM, add this to your dependencies:
 
 ```Groovy
-implementation 'com.google.cloud:google-cloud-spanner:6.31.2'
+implementation 'com.google.cloud:google-cloud-spanner:6.32.0'
 ```
 
 If you are using SBT, add this to your dependencies:
 
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-spanner" % "6.31.2"
+libraryDependencies += "com.google.cloud" % "google-cloud-spanner" % "6.32.0"
 ```
 
 ## Authentication