The ornamental design for a washing apparatus, as shown and described.
FIG. 1 is a left side perspective view of the washing apparatus;
FIG. 2 is a left side view;
FIG. 3 is a right side view;
FIG. 4 is a back view;
FIG. 5 is a front view;
FIG. 6 is a top view;
FIG. 7 is a bottom view; and,
FIG. 8 is a right side perspective view thereof.
The broken lines showing the hose connection portion are for the purpose of illustrating portions of the washing apparatus and form no part of the claimed design.