fix(update_version.py): fix pixi.toml version string substitution (#1846)

The update-version task was getting substituted too, we only want to sub the version string

Author: wpbonelli

distribution/update_version.py

@@ -336,7 +336,7 @@ def update_pixi(version: Version):
     tag = "version ="
     with open(path, "w") as fp:
         for line in lines:
-            if tag in line:
+            if line.startswith(tag):
                 line = f'{tag} "{version}"\n'
             fp.write(line)