[#1404] fix broken tests

Author: remkop

src/test/java/picocli/ArityTest.java

@@ -1662,7 +1662,7 @@ class App {
             new CommandLine(new App()).parseArgs("--implicit=false --explicit=false".split(" "));
             fail("--explicit option should not accept parameters");
         } catch (ParameterException ex) {
-            assertEquals("option '--explicit' (<explicit>) should be specified without 'false' parameter", ex.getMessage());
+            assertEquals("option '--explicit' should be specified without 'false' parameter", ex.getMessage());
         }
     }
 

src/test/java/picocli/CommandLineTest.java

@@ -1916,7 +1916,7 @@ class App {
             CommandLine.populateCommand(new App(), "-v", "-v");
             fail("expected exception");
         } catch (OverwrittenOptionException ex) {
-            assertEquals("option '-v' (<bool>) should be specified only once", ex.getMessage());
+            assertEquals("option '-v' should be specified only once", ex.getMessage());
         }
     }
 
@@ -1936,7 +1936,7 @@ class App {
             CommandLine.populateCommand(new App(), "-v", "--verbose");
             fail("expected exception");
         } catch (OverwrittenOptionException ex) {
-            assertEquals("option '--verbose' (<bool>) should be specified only once", ex.getMessage());
+            assertEquals("option '--verbose' should be specified only once", ex.getMessage());
         }
     }