Remove redundant now grgit Gradle plugin

The `grgit` Gradle plugin has been used to determine modified files to update their Copyright.
After migrating to a `-present` pattern we don't need to track modified files anymore.
Therefore, we don't need to manage `org.ajoberstar.grgit` plugin, too.

**Cherry-pick to `3.2.x`**

Author: artembilan

.github/dependabot.yml

@@ -20,7 +20,6 @@ updates:
         patterns:
           - org.gradle.*
           - io.spring.*
-          - org.ajoberstar.grgit
           - org.antora
           - io.micrometer:micrometer-docs-generator
           - com.willowtreeapps.assertk:assertk-jvm
@@ -63,7 +62,6 @@ updates:
           - org.gradle.*
           - com.github.spotbugs
           - io.spring.*
-          - org.ajoberstar.grgit
           - io.freefair.aggregate-javadoc
           - org.antora
           - io.micrometer:micrometer-docs-generator
@@ -75,52 +73,6 @@ updates:
   - package-ecosystem: github-actions
     target-branch: 3.2.x
     directory: /
-    schedule:
-      interval: weekly
-      day: saturday
-    labels:
-      - 'type: task'
-    groups:
-      development-dependencies:
-        patterns:
-          - '*'
-
-  - package-ecosystem: gradle
-    target-branch: 3.1.x
-    directory: /
-    schedule:
-      interval: monthly
-    ignore:
-      - dependency-name: '*'
-        update-types:
-          - version-update:semver-major
-          - version-update:semver-minor
-    open-pull-requests-limit: 10
-    labels:
-      - 'type: dependency-upgrade'
-    groups:
-      development-dependencies:
-        update-types:
-          - patch
-        patterns:
-          - org.gradle.*
-          - com.github.spotbugs
-          - io.spring.*
-          - org.ajoberstar.grgit
-          - io.freefair.aggregate-javadoc
-          - org.antora
-          - io.micrometer:micrometer-docs-generator
-          - com.willowtreeapps.assertk:assertk-jvm
-          - org.hibernate.validator:hibernate-validator
-          - org.apache.httpcomponents.client5:httpclient5
-          - org.awaitility:awaitility
-          - org.xerial.snappy:snappy-java
-          - org.lz4:lz4-java
-          - com.github.luben:zstd-jni
-
-  - package-ecosystem: github-actions
-    target-branch: 3.1.x
-    directory: /
     schedule:
       interval: weekly
       day: saturday

build.gradle

@@ -14,7 +14,6 @@ buildscript {
 plugins {
 	id 'base'
 	id 'idea'
-	id 'org.ajoberstar.grgit' version '5.3.2'
 	id 'io.spring.nohttp' version '0.0.11'
 	id 'io.spring.dependency-management' version '1.1.7' apply false
 	id 'org.antora' version '1.0.0'
@@ -33,14 +32,6 @@ ext {
 	linkScmConnection = 'git://github.com/spring-projects/spring-amqp.git'
 	linkScmDevConnection = '[email protected]:spring-projects/spring-amqp.git'
 
-	modifiedFiles =
-			files()
-					.from {
-						files(grgit.status().unstaged.modified)
-								.filter { f -> f.name.endsWith('.java') || f.name.endsWith('.kt') }
-					}
-	modifiedFiles.finalizeValueOnRead()
-
 	assertjVersion = '3.27.3'
 	assertkVersion = '0.28.1'
 	awaitilityVersion = '4.3.0'