build(deps): update dependency org.apache.maven.plugins:maven-compiler-plugin to v3.15.0

Author: renovate-bot

google-cloud-spanner-bom/pom.xml

@@ -100,7 +100,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.14.1</version>
+        <version>3.15.0</version>
         <configuration>
           <source>1.8</source>
           <target>1.8</target>

pom.xml

@@ -152,7 +152,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.14.1</version>
+        <version>3.15.0</version>
         <configuration>
           <source>1.8</source>
           <target>1.8</target>