Apply trailing slash normalization to remove_source as well

When sources are added with `add_trailing_slash`, the stored URI gets a
trailing slash. Without the same normalization on remove, users cannot
delete a source using the original URI they typed (without trailing slash).

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

Author: hsbt

lib/rubygems/commands/sources_command.rb

@@ -289,6 +289,7 @@ def execute
   end
 
   def remove_source(source_uri) # :nodoc:
+    source_uri = add_trailing_slash(source_uri)
     source = Gem::Source.new source_uri
 
     if configured_sources&.include? source

test/rubygems/test_gem_commands_sources_command.rb

@@ -864,7 +864,33 @@ def test_execute_remove_redundant_source_trailing_slash
     assert_equal false, Gem.sources.include?(source)
 
     expected = <<-EOF
-#{repo_without_slash} removed from sources
+#{repo_with_slash} removed from sources
+    EOF
+
+    assert_equal expected, @ui.output
+    assert_equal "", @ui.error
+  ensure
+    Gem.configuration.sources = nil
+  end
+
+  def test_execute_remove_without_trailing_slash
+    source_uri = "https://rubygems.pkg.github.com/my-org/"
+
+    Gem.configuration.sources = [source_uri]
+
+    setup_fake_source(source_uri)
+
+    @cmd.handle_options %W[--remove https://rubygems.pkg.github.com/my-org]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    source = Gem::Source.new source_uri
+    assert_equal false, Gem.sources.include?(source)
+
+    expected = <<-EOF
+#{source_uri} removed from sources
     EOF
 
     assert_equal expected, @ui.output