remove unnecessary pip_pre arg from tox.ini

tox.ini

@@ -1,13 +1,11 @@
 [tox]
 skipsdist = True
 envlist = unit, flake8, integration-spark-thrift
-pip_pre = true
 
 [testenv:{unit,py38,py39,py310,py}]
 allowlist_externals =
     /bin/bash
 commands = /bin/bash -c '{envpython} -m pytest -v {posargs} tests/unit'
-pip_pre = true
 passenv =
     DBT_*
     PYTEST_ADDOPTS
@@ -19,7 +17,6 @@ deps =
 allowlist_externals =
     /bin/bash
 basepython = python3.8
-pip_pre = true
 commands = /bin/bash -c '{envpython} -m pytest -v --profile databricks_http_cluster {posargs} -n4 tests/functional/adapter/*'
 passenv =
     DBT_*
@@ -33,7 +30,6 @@ deps =
 allowlist_externals =
     /bin/bash
 basepython = python3.8
-pip_pre = true
 commands = /bin/bash -c '{envpython} -m pytest -v --profile databricks_cluster {posargs} -n4 tests/functional/adapter/*'
 passenv =
     DBT_*
@@ -48,7 +44,6 @@ deps =
 allowlist_externals =
     /bin/bash
 basepython = python3.8
-pip_pre = true
 commands = /bin/bash -c '{envpython} -m pytest -v --profile databricks_sql_endpoint {posargs} -n4 tests/functional/adapter/*'
 passenv =
     DBT_*
@@ -64,7 +59,6 @@ deps =
 allowlist_externals =
     /bin/bash
 basepython = python3.8
-pip_pre = true
 commands = /bin/bash -c '{envpython} -m pytest -v --profile apache_spark {posargs} -n4 tests/functional/adapter/*'
 passenv =
     DBT_*
@@ -78,7 +72,6 @@ deps =
 allowlist_externals =
     /bin/bash
 basepython = python3.10
-pip_pre = true
 commands = /bin/bash -c '{envpython} -m pytest -v --profile spark_session {posargs} -n4 tests/functional/adapter/*'
 passenv =
     DBT_*