BSim: Extend warning message for existing signature files

[gemesa]

Fixes #8754

Before:

$ ./support/bsim generatesigs ghidra://localhost/repo-test ~/git-repos/bsim-xml --bsim postgresql://localhost/repo
openjdk version "21.0.4" 2024-07-16 LTS
OpenJDK Runtime Environment Temurin-21.0.4+7 (build 21.0.4+7-LTS)
OpenJDK 64-Bit Server VM Temurin-21.0.4+7 (build 21.0.4+7-LTS, mixed mode)
Max-Memory: 3.8 GBytes
Using configuration for:
 Database: repo
 Owner:    Example Owner

Repository Server: localhost
Password for gemesa:
Generating signatures for: obj1
WARN  Signature file already exists for: obj0 (SignatureRepository)

After:

$ ./support/bsim generatesigs ghidra://localhost/repo-test ~/git-repos/bsim-xml --bsim postgresql://localhost/repo
openjdk version "21.0.4" 2024-07-16 LTS
OpenJDK Runtime Environment Temurin-21.0.4+7 (build 21.0.4+7-LTS)
OpenJDK 64-Bit Server VM Temurin-21.0.4+7 (build 21.0.4+7-LTS, mixed mode)
Max-Memory: 3.8 GBytes
Using configuration for:
 Database: repo
 Owner:    Example Owner

Repository Server: localhost
Password for gemesa:
Generating signatures for: obj1
WARN  Signature file sigs_0de541a97a4cb9648d45f81f293de764 already exists for: obj0 (SignatureRepository)