Remove explicit references to Reactor Netty version

...now that 0.8 is also listed in the Reactor bom.

Issue: SPR-16387

build.gradle

@@ -239,9 +239,6 @@ configure(rootProject) {
 		imports {
 			mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		}
-		dependencies {
-			dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-		}
 		resolutionStrategy {
 			cacheChangingModulesFor 0, 'seconds'
 		}

spring-messaging/spring-messaging.gradle

@@ -7,9 +7,6 @@ dependencyManagement {
 		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		mavenBom "io.netty:netty-bom:${nettyVersion}"
 	}
-	dependencies {
-		dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-	}
 	resolutionStrategy {
 		cacheChangingModulesFor 0, 'seconds'
 	}

spring-test/spring-test.gradle

@@ -7,9 +7,6 @@ dependencyManagement {
 		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		mavenBom "io.netty:netty-bom:${nettyVersion}"
 	}
-	dependencies {
-		dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-	}
 	resolutionStrategy {
 		cacheChangingModulesFor 0, 'seconds'
 	}

spring-web/spring-web.gradle

@@ -8,9 +8,6 @@ dependencyManagement {
 		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		mavenBom "io.netty:netty-bom:${nettyVersion}"
 	}
-	dependencies {
-		dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-	}
 	resolutionStrategy {
 		cacheChangingModulesFor 0, 'seconds'
 	}

spring-webflux/spring-webflux.gradle

@@ -7,9 +7,6 @@ dependencyManagement {
 		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		mavenBom "io.netty:netty-bom:${nettyVersion}"
 	}
-	dependencies {
-		dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-	}
 	resolutionStrategy {
 		cacheChangingModulesFor 0, 'seconds'
 	}

spring-websocket/spring-websocket.gradle

@@ -7,9 +7,6 @@ dependencyManagement {
 		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
 		mavenBom "io.netty:netty-bom:${nettyVersion}"
 	}
-	dependencies {
-		dependency "io.projectreactor.netty:reactor-netty:0.8.0.BUILD-SNAPSHOT"
-	}
 	resolutionStrategy {
 		cacheChangingModulesFor 0, 'seconds'
 	}