fix: upgrade Go to 1.25.5 to address CVE-2025-61729 and CVE-2025-61727 (#2501)

This commit updates the Go version from 1.25.3 to 1.25.5 to fix two
security vulnerabilities in the Go standard library.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Signed-off-by: Juan Bustamante <[email protected]>
Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Author: jjbustamante

go.mod

@@ -156,4 +156,4 @@ require (
 
 replace github.com/BurntSushi/toml => github.com/BurntSushi/toml v1.3.2
 
-go 1.25.3
+go 1.25.5

tools/go.mod

@@ -2,7 +2,7 @@ module github.com/buildpacks/pack/tools
 
 go 1.25.0
 
-toolchain go1.25.3
+toolchain go1.25.5
 
 require (
 	github.com/golang/mock v1.6.0