Upgrade AWS Java SDK to 2.31.78

This picks up the fix for the locale bug reported at
aws/aws-sdk-java-v2#5968.

This reverts the patching of the library added in commit
2697a3a, except for the test
enhancement.

Fix confirmed in e.g. locale `ar-ER` with

    ./gradlew ":plugins:discovery-ec2:test" \
        --tests "org.elasticsearch.discovery.ec2.Ec2DiscoveryTests.testFilterByTags" \
        -Dtests.seed=596874EED28A2B92 -Dtests.locale=ar-ER -Dtests.timezone=NET \
        -Druntime.java=24

Author: DaveCTurner

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/dependencies/patches/awsv2sdk/Awsv2ClassPatcher.java

@@ -17,7 +17,7 @@ jna               = 5.12.1
 netty             = 4.1.118.Final
 commons_lang3     = 3.9
 google_oauth_client = 1.34.1
-awsv2sdk            = 2.30.38
+awsv2sdk            = 2.31.78
 reactive_streams    = 1.0.4
 
 antlr4            = 4.13.1