Prepare prerelease 0.7.2-alpha2 (#282)

Bump version to 0.7.2-alpha2

## Motivation and Context
New prerelease version with signing fixes 

## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

build.gradle.kts

@@ -6,7 +6,7 @@ plugins {
 
 allprojects {
     group = "io.modelcontextprotocol"
-    version = "0.7.2-alpha1"
+    version = "0.7.2-alpha2"
 }
 
 dependencies {

gradle/libs.versions.toml

@@ -20,7 +20,7 @@ kotest = "6.0.3"
 awaitility = "4.3.0"
 
 # Samples
-mcp-kotlin = "0.7.2-alpha1"
+mcp-kotlin = "0.7.2-alpha2"
 anthropic = "2.7.0"
 shadow = "8.1.1"