[fix] remove unused aiplugin references (#8780)

As per our conversation, these dependencies are unused and are causing
(**intermittent** 😬) presubmit failures, with errors like:

Could not resolve
bundledPlugin:com.google.tools.ij.aiplugin:AI-252.25557.131.2521.14240541.


---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

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  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide]([https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md)
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Author: pq

build.gradle.kts

@@ -218,7 +218,6 @@ dependencies {
     // https://plugins.jetbrains.com/docs/intellij/plugin-dependencies.html#project-setup
     bundledPlugins(
       immutableListOf(
-        "com.google.tools.ij.aiplugin",
         "com.intellij.java",
         "com.intellij.properties",
         "JUnit",

resources/META-INF/plugin.xml

@@ -37,9 +37,6 @@
   <depends optional="true" config-file="idea-contribs.xml">com.intellij.modules.java</depends>
   <depends optional="true" config-file="flutter-coverage.xml">com.intellij.modules.coverage</depends>
 
-  <!-- Contributes Gemini Code Assist extensions. -->
-  <depends optional="true" config-file="gemini-contribs.xml">com.google.tools.ij.aiplugin</depends>
-
   <!-- Contributes Android-supported features and implementations. -->
   <depends optional="true" config-file="android-contribs.xml">org.jetbrains.android</depends>