Don't indent an indented `# isort: assignments` block twice

`literal.assignments` kept each line's indentation as part of the variable name, and `process` then indents the sorted block by the action comment's indentation again, so inside a class or function the assignments came out one level too deep. The other sort types strip the name already. Strip the indentation here too.

isort/literal.py

diff --git a/isort/literal.py b/isort/literal.py
index 3be7f7c..57027d2 100644
--- a/isort/literal.py
+++ b/isort/literal.py
@@ -20,7 +20,7 @@
             continue
         if " = " not in line:
             raise AssignmentsFormatMismatch(code)
-        variable_name, value = line.split(" = ", 1)
+        variable_name, value = line.lstrip().split(" = ", 1)
         values[variable_name] = value
 
     return "".join(

tests/unit/test_regressions.py

diff --git a/tests/unit/test_regressions.py b/tests/unit/test_regressions.py
index 6a28d46..1d21c9c 100644
--- a/tests/unit/test_regressions.py
+++ b/tests/unit/test_regressions.py
@@ -3065,3 +3065,9 @@
     )
     assert isort.code(code) == expected
     assert isort.code(expected) == expected
+
+
+def test_isort_assignments_in_an_indented_block_keeps_its_indentation() -> None:
+    """The sorted assignments were indented a second time, which broke the code."""
+    test_input = "class C:\n    # isort: assignments\n    b = 1\n    a = 2\n"
+    assert isort.code(test_input) == "class C:\n    # isort: assignments\n    a = 2\n    b = 1\n"