Enable RSpec profiling only if RSPEC_PROFILING_POSTGRES_URL is not empty

What does this MR do?

This ensures RSpec profiling is not enabled if the RSPEC_PROFILING_POSTGRES_URL secret variable exists but is empty.

What are the relevant issue numbers?

Closes #31933 (closed)

config/initializers/rspec_profiling.rb

@@ -32,7 +32,7 @@ end
 if Rails.env.test?
   RspecProfiling.configure do |config|
-    if ENV['RSPEC_PROFILING_POSTGRES_URL']
+    if ENV['RSPEC_PROFILING_POSTGRES_URL'].present?
       RspecProfiling::Collectors::PSQL.prepend(RspecProfilingExt::PSQL)
       config.collector = RspecProfiling::Collectors::PSQL
     end