update fiddle requirement to 0.2.6

Author: aireenmei

praxis/pip_package/requirements.txt

@@ -87,7 +87,7 @@ executing==1.2.0
     # via stack-data
 fastjsonschema==2.16.3
     # via nbformat
-fiddle==0.2.5
+fiddle==0.2.6
     # via -r praxis-requirements.in
 flatbuffers==1.12
     # via tensorflow

requirements.in

@@ -4,7 +4,7 @@
 absl-py==1.4.0
 clu==0.0.8
 einops==0.6.0
-fiddle==0.2.5
+fiddle==0.2.6
 flax==0.6.8
 jax==0.4.7
 jax-bitempered-loss==0.0.2