Fix default client.ping.timeout value in docs

[KyleAure]

Docs were never updated when the default value of client.ping.timeout was updated from 5 to 10 seconds.

testcontainers-java/core/src/main/java/org/testcontainers/utility/TestcontainersConfiguration.java

Lines 223 to 225 in 7351b66

	public Integer getClientPingTimeout() {
	return Integer.parseInt(getEnvVarOrProperty("client.ping.timeout", "10"));
	}

[eddumelendez]

great catch, @KyleAure ! Thanks for your contribution.