[ruby/rubygems] Use eq matcher instead of be for string comparison in newgem template

be checks object identity which will fail for newly-allocated strings.
eq checks value equality and is the correct matcher here.

ruby/rubygems@828440937b

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

lib/bundler/templates/newgem/spec/newgem_spec.rb.tt

@@ -9,7 +9,7 @@ RSpec.describe <%= config[:constant_name] %> do
   it "can call into Rust" do
     result = <%= config[:constant_name] %>.hello("world")
 
-    expect(result).to be("Hello world, from Rust!")
+    expect(result).to eq("Hello world, from Rust!")
   end
 <%- else -%>
   it "does something useful" do