add deprecation date for holesky, classic, mordor networks

[macfarla]

PR description

Fixed Issue(s)

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• Considered documentation and added the doc-change-required label to this PR if updates are required.
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• hive tests: Engine or other RPCs modified?

[macfarla]

2025-11-14 14:50:24.459+1000 | main | WARN  | Besu |
####################################################################################################
#                                                                                                  #
#                  ETC Classic support in Besu is deprecated as of November 2025                   #
#                                                                                                  #
####################################################################################################

[macfarla]

added label but I also created a ticket to update docs hyperledger/besu-docs#1861

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