[SPARK-37050][PYTHON] Update Conda installation instructions
[SPARK-37050][PYTHON] Update Conda installation instructions

### What changes were proposed in this pull request?

Improve conda installation docs

### Why are the changes needed?

As requested [here](https://github.com/apache/spark-website/pull/361#issuecomment-945660978). Ideally, this should be backported to the 3.2-branch (so it becomes visible for the 3.2.0 installation documentation [here](https://spark.apache.org/docs/3.2.0/api/python/getting_started/install.html)).
CC gengliangwang

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Not tested

Closes #34315 from h-vetinari/conda-install.

Lead-authored-by: H. Vetinari <1f31c171534ec271a8ad1f6a09365539fad71d16@gmx.com>
Co-authored-by: h-vetinari <1f31c171534ec271a8ad1f6a09365539fad71d16@gmx.com>
Signed-off-by: Hyukjin Kwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>
(cherry picked from commit 016ab0c6f2e5d29a2df08bc6d5e2bb7240a6577a)
Signed-off-by: Hyukjin Kwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>

milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark