Fix net-http deprecation warning for Ruby 3.4

This old constant was deprecated in 2001 and will now be removed in Ruby 3.5

On Ruby 3.4, removing a deprecated constant will warn:

> /home/user/code/webmock/lib/webmock/http_lib_adapters/net_http.rb:55: warning: constant Net::HTTPSession is deprecated

It fixes this error on Ruby 3.5:
```
/usr/local/bundle/bundler/gems/webmock-9ff63ac7c845/lib/webmock/http_lib_adapters/net_http.rb:25:in 'Module#remove_const': constant Net::HTTPSession not defined (NameError)

        Net.send(:remove_const, :HTTPSession)
           ^^^^^
	from /usr/local/bundle/bundler/gems/webmock-9ff63ac7c845/lib/webmock/http_lib_adapters/net_http.rb:25:in 'WebMock::HttpLibAdapters::NetHttpAdapter.disable!'
```

lib/webmock/http_lib_adapters/net_http.rb

@@ -12,19 +12,25 @@ class NetHttpAdapter < HttpLibAdapter
       adapter_for :net_http
 
       OriginalNetHTTP = Net::HTTP unless const_defined?(:OriginalNetHTTP)
+      # This will be removed in Ruby 3.5. In Ruby 3.4, const_remove will warn.
+      HAS_LEGACY_CONSTANT = Net.const_defined?(:HTTPSession)
 
       def self.enable!
         Net.send(:remove_const, :HTTP)
-        Net.send(:remove_const, :HTTPSession)
         Net.send(:const_set, :HTTP, @webMockNetHTTP)
-        Net.send(:const_set, :HTTPSession, @webMockNetHTTP)
+        if HAS_LEGACY_CONSTANT
+          remove_silently(Net, :HTTPSession)
+          Net.send(:const_set, :HTTPSession, @webMockNetHTTP)
+        end
       end
 
       def self.disable!
         Net.send(:remove_const, :HTTP)
-        Net.send(:remove_const, :HTTPSession)
         Net.send(:const_set, :HTTP, OriginalNetHTTP)
-        Net.send(:const_set, :HTTPSession, OriginalNetHTTP)
+        if HAS_LEGACY_CONSTANT
+          remove_silently(Net, :HTTPSession)
+          Net.send(:const_set, :HTTPSession, OriginalNetHTTP)
+        end
 
         #copy all constants from @webMockNetHTTP to original Net::HTTP
         #in case any constants were added to @webMockNetHTTP instead of Net::HTTP
@@ -37,6 +43,14 @@ def self.disable!
         end
       end
 
+      def self.remove_silently(mod, const) #:nodoc:
+        # Don't warn on removing the deprecated constant
+        verbose, $VERBOSE = $VERBOSE, nil
+        mod.send(:remove_const, const)
+      ensure
+        $VERBOSE = verbose
+      end
+
       @webMockNetHTTP = Class.new(Net::HTTP) do
         class << self
           def socket_type