Do not quote classes we fail to load

The error message used to be
  failed to load class 'Test'
This commit makes it
  failed to load class Test
The reasoning is that there is no need to quote the class name, it is
totally clear where it starts and where it ends.

jbmc/regression/jbmc/classpath-invalid/test-jar.desc

@@ -4,7 +4,7 @@ Test.class
 ^EXIT=6$
 ^SIGNAL=0$
 ^the program has no entry point$
-^failed to load class 'Test'$
+^failed to load class Test$
 --
 --
 symex-driven lazy loading should emit "the program has no entry point" but currently doesn't

jbmc/regression/jbmc/classpath-invalid/test-path.desc

@@ -4,7 +4,7 @@ Test.class
 ^EXIT=6$
 ^SIGNAL=0$
 ^the program has no entry point$
-^failed to load class 'Test'$
+^failed to load class Test$
 --
 --
 symex-driven lazy loading should emit "the program has no entry point" but currently doesn't

jbmc/regression/jbmc/generics_type_param/test.desc

@@ -7,6 +7,6 @@ Reading class AWrapper
 Reading class FWrapper
 Reading class IWrapper
 --
-failed to load class \'AWrapper\'
-failed to load class \'FWrapper\'
-failed to load class \'IWrapper\'
+failed to load class AWrapper
+failed to load class FWrapper
+failed to load class IWrapper

jbmc/src/java_bytecode/java_class_loader.cpp

@@ -176,7 +176,7 @@ java_class_loadert::get_parse_tree(
     return parse_trees;
 
   // Not found or failed to load
-  warning() << "failed to load class \'" << class_name << '\'' << eom;
+  warning() << "failed to load class " << class_name << eom;
   parse_trees.emplace_back(class_name);
   return parse_trees;
 }