Revert "Ignore x-amz-checksum-algorithm when checking for user suppli…

…ed checksums."

This reverts commit 93a47eb.

botocore/utils.py

@@ -185,7 +185,7 @@
 
 # This pattern can be used to detect if a header is a flexible checksum header
 CHECKSUM_HEADER_PATTERN = re.compile(
-    r'^x-amz-checksum-(?!algorithm\b)([a-z0-9]*)$',
+    r'^X-Amz-Checksum-([a-z0-9]*)$',
     flags=re.IGNORECASE,
 )
 

tests/unit/test_httpchecksum.py

@@ -259,28 +259,6 @@ def test_request_checksum_algorithm_model_new_crc32(self):
         }
         self.assertEqual(actual_algorithm, expected_algorithm)
 
-    def test_x_amz_checksum_algorithm_header_is_ignored(self):
-        request = self._build_request(b"")
-        request["headers"]["x-amz-checksum-algorithm"] = "some_value"
-        operation_model = self._make_operation_model(
-            http_checksum={"requestAlgorithmMember": "Algorithm"}
-        )
-        params = {}
-
-        resolve_request_checksum_algorithm(request, operation_model, params)
-        self.assertIn("checksum", request["context"])
-
-    def test_non_x_amz_checksum_algorithm_header_is_not_ignored(self):
-        request = self._build_request(b"")
-        request["headers"]["x-amz-checksum-someChecksum"] = "some_value"
-        operation_model = self._make_operation_model(
-            http_checksum={"requestAlgorithmMember": "Algorithm"}
-        )
-        params = {}
-
-        resolve_request_checksum_algorithm(request, operation_model, params)
-        self.assertNotIn("checksum", request["context"])
-
     def test_apply_request_checksum_handles_no_checksum_context(self):
         request = self._build_request(b"")
         apply_request_checksum(request)