Allow TODO in code

Don't reject TODO in code. Fix #2587

tests/scripts/check-files.py

@@ -6,7 +6,7 @@
 """
 This script checks the current state of the source code for minor issues,
 including incorrect file permissions, presence of tabs, non-Unix line endings,
-trailing whitespace, presence of UTF-8 BOM, and TODO comments.
+trailing whitespace, and presence of UTF-8 BOM.
 Note: requires python 3, must be run from Mbed TLS root.
 """
 
@@ -168,19 +168,6 @@ class MergeArtifactIssueTracker(LineIssueTracker):
             return True
         return False
 
-class TodoIssueTracker(LineIssueTracker):
-    """Track lines containing ``TODO``."""
-
-    heading = "TODO present:"
-    files_exemptions = frozenset([
-        os.path.basename(__file__),
-        "benchmark.c",
-        "pull_request_template.md",
-    ])
-
-    def issue_with_line(self, line, _filepath):
-        return b"todo" in line.lower()
-
 
 class IntegrityChecker(object):
     """Sanity-check files under the current directory."""
@@ -209,7 +196,6 @@ class IntegrityChecker(object):
             TrailingWhitespaceIssueTracker(),
             TabIssueTracker(),
             MergeArtifactIssueTracker(),
-            TodoIssueTracker(),
         ]
 
     @staticmethod