Remove didCharSizeChange logic from renderer

The only thing `didCharSizeChange` was used for was to figure out if we
need to refresh the character atlas or not. However, `acquireCharAtlas`
already inspects the atlas owned by this terminal, and if it matches, it
avoids generating a new atlas.

So if `didCharSizeChange` is true and it's not needed, it quickly bails
out as a no-op. But if `didCharSizeChange` is false, and it was needed
(possible given the complexity of testing all of these edge cases), it
could introduce a bug.

I think it makes sense to just get rid of `didCharSizeChange`, and just
always call `acquireCharAtlas`.

src/renderer/TextRenderLayer.ts

@@ -27,8 +27,8 @@ export class TextRenderLayer extends BaseRenderLayer {
     this._state = new GridCache<CharData>();
   }
 
-  public resize(terminal: ITerminal, dim: IRenderDimensions, charSizeChanged: boolean): void {
-    super.resize(terminal, dim, charSizeChanged);
+  public resize(terminal: ITerminal, dim: IRenderDimensions): void {
+    super.resize(terminal, dim);
 
     // Clear the character width cache if the font or width has changed
     const terminalFont = this._getFont(terminal, false);