doc(fix): GaussiamBeam: beam_distance -> waist_distance

Author: FilipeFcp

tidy3d/components/source/field.py

@@ -584,7 +584,7 @@ class GaussianBeam(AngledFieldSource, PlanarSource, BroadbandSource):
         title="Waist Distance",
         description="Distance from the beam waist along the propagation direction. "
         "A positive value means the waist is positioned behind the source, considering the propagation direction. "
-        "For example, for a beam propagating in the ``+`` direction, a positive value of ``beam_distance`` "
+        "For example, for a beam propagating in the ``+`` direction, a positive value of ``waist_distance`` "
         "means the beam waist is positioned in the ``-`` direction (behind the source). "
         "A negative value means the beam waist is in the ``+`` direction (in front of the source). "
         "For an angled source, the distance is defined along the rotated propagation direction.",