Fix Apache snapshot repo usage

[adoroszlai]

What changes were proposed in this pull request?

Problem: Beam build searches repository.apache.org for artifacts not to be found there. (See also #33333.)

Repro:

$ rm -fr ~/.gradle/caches
$ ./gradlew --info sdks:java:io:kafka:compileJava
...
Resource missing. [HTTP GET: https://repository.apache.org/snapshots/io/confluent/kafka-avro-serializer/7.5.5/kafka-avro-serializer-7.5.5.pom]
Resource missing. [HTTP GET: https://repository.apache.org/snapshots/io/confluent/kafka-schema-registry-client/7.5.5/kafka-schema-registry-client-7.5.5.pom]
Resource missing. [HTTP GET: https://repository.apache.org/content/repositories/releases/io/confluent/kafka-schema-registry-client/7.5.5/kafka-schema-registry-client-7.5.5.pom]
Resource missing. [HTTP GET: https://repository.apache.org/content/repositories/releases/io/confluent/kafka-avro-serializer/7.5.5/kafka-avro-serializer-7.5.5.pom]
...

Fix:

1. Limit repository.apache.org/snapshots to snapshot artifacts.
2. Move Confluent repo definition before the Apache repos.

How was this patch tested?

$ rm -fr ~/.gradle/caches
$ ./gradlew --info sdks:java:io:kafka:compileJava | tee gradle.log 2>&1

$ grep -c 'HTTP GET.*repository.apache.org' gradle.log
0

$ grep 'packages.confluent' gradle.log
Downloading https://packages.confluent.io/maven/io/confluent/kafka-schema-registry-client/7.5.5/kafka-schema-registry-client-7.5.5.pom to ...
Downloading https://packages.confluent.io/maven/io/confluent/kafka-avro-serializer/7.5.5/kafka-avro-serializer-7.5.5.pom to ...
...

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[adoroszlai]

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[Abacn]

great, thanks for the fix!

[adoroszlai]

Thanks @Abacn for reviewing and merging this.