fix(build): align ai-pii module parent versions with 2.7.3-SNAPSHOT - #8111

Problem

master currently cannot be built from the repository root: two newly added modules still declare their parent version as 2.7.2-SNAPSHOT, while the root project is now 2.7.3-SNAPSHOT. Maven fails while reading the reactor, before compiling anything:

[FATAL] Non-resolvable parent POM for org.apache.shenyu:shenyu-plugin-ai-pii:2.7.2-SNAPSHOT:
        Could not find artifact org.apache.shenyu:shenyu-plugin-ai:pom:2.7.2-SNAPSHOT
[FATAL] Non-resolvable parent POM for org.apache.shenyu:shenyu-spring-boot-starter-plugin-ai-pii:2.7.2-SNAPSHOT:
        Could not find artifact org.apache.shenyu:shenyu-spring-boot-starter-plugin:pom:2.7.2-SNAPSHOT

This is currently red on master and on every PR targeting it — e.g. rat_check, pr_build and the aggregate build gate fail in ~20s while reading the POMs.

Cause: #8100 (prepare release v2.7.2) bumped the root to 2.7.3-SNAPSHOT at 2026-10-26T05:55:56Z, and #8105 (policy-driven PII detection for AI traffic) was merged at 05:56:40Z adding these two modules pinned to 2.7.2-SNAPSHOT.

Fix

Bump the two parent version declarations to 2.7.3-SNAPSHOT:

• shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-pii/pom.xml
• shenyu-spring-boot-starter/shenyu-spring-boot-starter-plugin/shenyu-spring-boot-starter-plugin-ai-pii/pom.xml

No other stale 2.7.2-SNAPSHOT references exist in the reactor (git grep "2.7.2-SNAPSHOT" -- '**/pom.xml' returns nothing after this change).

Validation

• ./mvnw -pl shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-pii validate → BUILD SUCCESS (reactor POMs are readable again, shenyu-plugin-ai-pii 2.7.3-SNAPSHOT is built, checkstyle passes).
• Before the change the same command fails with the Non-resolvable parent POM error above.