fix: include an explicit version for javax-annotations-api (#261)

The Maven flatten plugin transforms the pom of the project from a set of imports and transitive dependencies into a pom that contains all dependencies and versions explicitly. This process did however miss the javax-annotations-api dependency that is only included for JDK9 and higher. Fixes GoogleCloudPlatform/java-docs-samples#3139

Author: olavloite

google-cloud-spanner-bom/pom.xml

@@ -90,7 +90,7 @@
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-spanner</artifactId>
  <type>test-jar</type>
- <version>1.55.1</version><!-- {x-version-update:google-cloud-spanner:current} -->
+ <version>1.55.2-SNAPSHOT</version><!-- {x-version-update:google-cloud-spanner:current} -->
  </dependency>
  <dependency>
  <groupId>com.google.api.grpc</groupId>

google-cloud-spanner/pom.xml

@@ -336,6 +336,7 @@
  <dependency>
  <groupId>javax.annotation</groupId>
  <artifactId>javax.annotation-api</artifactId>
+ <version>1.3.2</version>
  </dependency>
  </dependencies>
  </profile>

grpc-google-cloud-spanner-v1/pom.xml

@@ -53,6 +53,7 @@
  <dependency>
  <groupId>javax.annotation</groupId>
  <artifactId>javax.annotation-api</artifactId>
+ <version>1.3.2</version>
  </dependency>
  </dependencies>
  </profile>