Exclude some tests which are failing due to a rubygems version mismatch

The ruby-rubygems version diverges from what ruby upstream has embedded
in its code.

Author: lucaskanashiro

debian/tests/excludes/autopkgtest/TestGem.rb

@@ -10,3 +10,4 @@
 exclude :test_use_gemdeps_automatic, 'failure against ruby2.7, cant find gem bundler (= 2.1.2)'
 exclude :test_self_use_gemdeps, 'failure against ruby2.7, cant find gem bundler (= 2.1.2)'
 exclude :test_use_gemdeps_specific, 'failure against ruby2.7, cant find gem bundler (= 2.1.2)'
+exclude :test_use_gemdeps_missing_gem, 'failure against ruby-rubygems, version mismatch'

debian/tests/excludes/autopkgtest/TestGemInstaller.rb

@@ -9,3 +9,4 @@
 exclude :test_default_gem_without_wrappers, 'failure against ruby2.7, expects path /var/lib/gems/2.7.0/specifications/default to exist'
 exclude :test_default_gem_with_exe_as_bindir, 'failure against ruby2.7, expects path /var/lib/gems/2.7.0/specifications/default to exist'
 exclude :test_install_creates_binstub_that_prefers_user_installed_gem_to_default, 'failure against ruby2.7, needs further investigation'
+exclude :test_app_script_text, 'failure against ruby-rubygems, version mismatch'

debian/tests/excludes/autopkgtest/TestGemSpecification.rb

@@ -1 +1,3 @@
 exclude :test_base_dir_default, 'depends on source tree'
+exclude :test_self_from_yaml_cleans_up_defaultkey, 'failure against ruby-rubygems, version mismatch'
+exclude :test_self_from_yaml_cleans_up_defaultkey_from_newer_192, 'failure against ruby-rubygems, version mismatch'