Revert "Resolve symlinks to cipd, vpython3"

This reverts commit c962e86f7b.

Reason for revert: broke MacOS:
realpath: command not found

Original change's description:
> Resolve symlinks to cipd, vpython3
>
> If we point a symlink at vpython3 (or various other tools), it will try
> to resolve the depot_tools path to wherever that symlink is stored. We
> should instead follow the symlink before determining the path.
>
> Prior art:
>
> * in python, we're doing Path.resolve() in many cases
> * in shell, there's a "$(readlink "$(dirname "$0"))" (man/push_to_gs.sh)
>
> BUG=b:270994985
> TEST=symlink to vpython3 works
>
> Change-Id: Ifee014d2571ccf58d830a2702c8a0ea225dd4821
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4295094
> Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
> Commit-Queue: Brian Norris <briannorris@chromium.org>

Bug: b:270994985
Change-Id: I69342f3a52153b8cb1ed4366ede5883dfe5ec0b9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4310530
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

cipd

@@ -6,7 +6,7 @@
 
 set -e -o pipefail
 
-MYPATH=$(dirname "$(realpath "${BASH_SOURCE[0]}")")
+MYPATH=$(dirname "${BASH_SOURCE[0]}")
 CYGWIN=false
 
 # Make sure this starts empty

vpython3

@@ -34,7 +34,7 @@ then
 fi
 
 
-base_dir=$(dirname "$(realpath "$0")")
+base_dir=$(dirname "$0")
 
 source "$base_dir/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null