[fix](regression) keep variant_doc_mode_p2 load in the p2 group with its queries

[shuke987]

What problem does this PR solve?

In regression_test_variant_doc_mode_p2, load.groovy (which creates and loads the github_events table) is tagged nonConcurrent,p2, while the 76 sql/*.sql query cases in the same directory fall back to the path-derived default group variant_doc_mode_p2 (no nonConcurrent).

nonConcurrent is a separate pipeline, so the load step and the queries get routed to different runs/clusters. In the P2 run the load never executes, and every query fails instantly with:

Table [github_events] does not exist in database [regression_test_variant_doc_mode_p2]

This produced 66 cascade failures in a single branch-4.1 P2 build (e.g. build #35 / 198091), all from the same root cause.

Root cause

The nonConcurrent tag was applied only to load.groovy, not to the dependent queries. The correct nonConcurrent sibling (variant_github_events_nonConcurrent_p2) encodes it in the directory name so the whole suite (load + queries) routes together; variant_doc_mode_p2 instead split the data-prep away from its queries.

The load only sets session variables and does no global-state mutation (no set global / FE-BE config / debug points), so it does not actually need nonConcurrent isolation.

Fix

Drop nonConcurrent so load.groovy shares the p2 group/pipeline with its queries. load.groovy sorts before sql/, runs first, and github_events is present when the queries execute.

-suite("test_doc_value_p2", "nonConcurrent,p2"){
+suite("test_doc_value_p2", "p2"){

Note: the identical structure exists on master (#59183); a follow-up there is advisable.

Release note

None

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