Add test for copyright detection without year

Signed-off-by: Krishkumar Saini <k36570322@gmail.com>

Author: arjun23009

tests/textcode/copyright_no_year.expected.json

@@ -0,0 +1 @@
+[]

tests/textcode/copyright_no_year.txt

@@ -0,0 +1 @@
+Copyright The OpenTelemetry Authors

tests/textcode/test_strings.py

@@ -180,3 +180,11 @@ def test_strings_with_lf(self):
         test_file = 'strings/with-lf/strings.exe'
         expected_file = 'strings/with-lf/strings.exe.results'
         self.check_file_strings(test_file, expected_file, regen=REGEN_TEST_FIXTURES)
+    
+    class TestStrings(FileBasedTesting):
+  
+        def test_copyright_without_year(self):
+                self.check_file_strings(
+            test_file='copyright_no_year.txt',
+            expected_file='copyright_no_year.expected.json'
+        )