CI: partially revert #17065, un-pin pyarrow on some builds

Author: jreback

ci/requirements-2.7_BUILD_TEST.sh

@@ -4,4 +4,4 @@ source activate pandas
 
 echo "install 27 BUILD_TEST"
 
-conda install -n pandas -c conda-forge pyarrow=0.4.1 dask
+conda install -n pandas -c conda-forge pyarrow dask

ci/requirements-3.6.run

@@ -15,7 +15,7 @@ jinja2
 sqlalchemy
 pymysql
 feather-format
-pyarrow=0.4.1
+pyarrow
 # psycopg2 (not avail on defaults ATM)
 beautifulsoup4
 s3fs

ci/requirements-3.6_DOC.sh

@@ -6,6 +6,6 @@ echo "[install DOC_BUILD deps]"
 
 pip install pandas-gbq
 
-conda install -n pandas -c conda-forge feather-format pyarrow=0.4.1 nbsphinx pandoc
+conda install -n pandas -c conda-forge feather-format pyarrow nbsphinx pandoc
 
 conda install -n pandas -c r r rpy2 --yes

ci/requirements-3.6_WIN.run

@@ -8,7 +8,7 @@ xlrd
 xlwt
 scipy
 feather-format
-pyarrow=0.4.1
+pyarrow
 numexpr
 pytables
 matplotlib

pandas/util/_print_versions.py

@@ -69,6 +69,7 @@ def show_versions(as_json=False):
         ("Cython", lambda mod: mod.__version__),
         ("numpy", lambda mod: mod.version.version),
         ("scipy", lambda mod: mod.version.version),
+        ("pyarrow", lambda mod: mod.__version__),
         ("xarray", lambda mod: mod.__version__),
         ("IPython", lambda mod: mod.__version__),
         ("sphinx", lambda mod: mod.__version__),
@@ -95,7 +96,6 @@ def show_versions(as_json=False):
         ("s3fs", lambda mod: mod.__version__),
         ("pandas_gbq", lambda mod: mod.__version__),
         ("pandas_datareader", lambda mod: mod.__version__),
-        ("pyarrow", lambda mod: mod.__version__),
     ]
 
     deps_blob = list()