Unpin pandas

Fixes #3680; this pin was added in #136: https://github.com/flyteorg/flytekit/pull/136/files#diff-60f61ab7a8d1910d86d9fda2261620314edcae5894d5aaa236b821c7256badd7R18 ~3 years ago when the latest pandas version was 1.2.1; flytekit is not using any features that have broken any of its tests in upgrading to use pandas >=2.0.0

setup.py

@@ -31,7 +31,7 @@
  "googleapis-common-protos>=1.57",
  "flyteidl>=1.5.16",
  "wheel>=0.30.0,<1.0.0",
- "pandas>=1.0.0,<2.0.0",
+ "pandas",
  "pyarrow>=4.0.0,<11.0.0",
  "click>=6.6,<9.0",
  "croniter>=0.3.20,<4.0.0",