spec: suppress deprecations of "lambda(&proc_block)" pattern

spec/ruby/language/lambda_spec.rb

@@ -348,7 +348,9 @@ describe "A lambda expression 'lambda { ... }'" do
   end
 
   it "requires a block" do
-    lambda { lambda }.should raise_error(ArgumentError)
+    suppress_warning do
+      lambda { lambda }.should raise_error(ArgumentError)
+    end
   end
 
   it "may include a rescue clause" do
@@ -375,9 +377,11 @@ describe "A lambda expression 'lambda { ... }'" do
     ruby_version_is "2.7" do
       it "raises ArgumentError" do
         implicit_lambda = nil
-        -> {
-          meth { 1 }
-        }.should raise_error(ArgumentError, /tried to create Proc object without a block/)
+        suppress_warning do
+          -> {
+            meth { 1 }
+          }.should raise_error(ArgumentError, /tried to create Proc object without a block/)
+        end
       end
     end
   end