MLBEDSW-3367 Update pre-commit flake8 version

Update the version of flake8 used in pre-commit to facilitate
adding mypy to pre-commit.

Signed-off-by: Jonas Ohlsson <jonas.ohlsson@arm.com>
Change-Id: I457dec87b77487ca6f14ff4a679c4cc927b272b0
diff --git a/ethosu/vela/softmax.py b/ethosu/vela/softmax.py
index 13ca319..711c1e0 100644
--- a/ethosu/vela/softmax.py
+++ b/ethosu/vela/softmax.py
@@ -501,9 +501,7 @@
         reciprocal_right_shift = add_op_get_ofm(create_sub(name, const_31, headroom_plus_one, no_scale_quant))
 
         # PASS 7 - SHL
-        one = create_const_tensor(
-            f"one_const", [1, 1, 1, 1], DataType.int32, [1], np.int32, quantization=no_scale_quant
-        )
+        one = create_const_tensor("one_const", [1, 1, 1, 1], DataType.int32, [1], np.int32, quantization=no_scale_quant)
         constant_one = add_op_get_ofm(
             create_shl(f"{self.op.name}_shl{pass_number}", one, reciprocal_right_shift, no_scale_quant)
         )