style: replace em dashes with colons in async-geotiff quickstart prose

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: aboydnw

quickstarts/async-geotiff.ipynb

@@ -145,7 +145,7 @@
        " - E[east]: Easting (metre)\n",
        " - N[north]: Northing (metre)\n",
        " Area of Use:\n",
-       " - name: Between 126\u00b0W and 120\u00b0W, northern hemisphere between equator and 84\u00b0N, onshore and offshore. Canada - British Columbia (BC); Northwest Territories (NWT); Nunavut; Yukon. United States (USA) - Alaska (AK).\n",
+       " - name: Between 126°W and 120°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); Northwest Territories (NWT); Nunavut; Yukon. United States (USA) - Alaska (AK).\n",
        " - bounds: (-126.0, 0.0, -120.0, 84.0)\n",
        " Coordinate Operation:\n",
        " - name: UTM zone 10N\n",
@@ -302,7 +302,7 @@
        "version_minor": 0
       },
       "text/plain": [
-       "VBox(children=(<lonboard._map.Map object at 0x7acbdc6bb800>, VBox(children=(ErrorOutput(), ErrorOutput(), Erro\u2026"
+       "VBox(children=(<lonboard._map.Map object at 0x7acbdc6bb800>, VBox(children=(ErrorOutput(), ErrorOutput(), Erro…"
       ]
      },
      "execution_count": 8,
@@ -371,11 +371,11 @@
     "\n",
     "If every cell above produced its expected result, async-geotiff is wired up end-to-end:\n",
     "\n",
-    "- **No GDAL** \u2014 pip-installed, no system deps\n",
-    "- **Async-first** \u2014 64 parallel window reads in one `gather`\n",
-    "- **Zero-copy** \u2014 array data is a NumPy view onto the decoded buffer\n",
-    "- **Type-hinted** \u2014 full autocomplete on `GeoTIFF`, `Window`, `Array`\n",
-    "- **Overview-aware** \u2014 picked overview `[0]` for full resolution explicitly\n",
+    "- **No GDAL**: pip-installed, no system deps\n",
+    "- **Async-first**: 64 parallel window reads in one `gather`\n",
+    "- **Zero-copy**: array data is a NumPy view onto the decoded buffer\n",
+    "- **Type-hinted**: full autocomplete on `GeoTIFF`, `Window`, `Array`\n",
+    "- **Overview-aware**: picked overview `[0]` for full resolution explicitly\n",
     "\n",
     "For resampling or reprojection, hand the array to [rasterio](https://rasterio.readthedocs.io/) via an in-memory file. For browser-side rendering of the same data, see the [Lonboard tutorial](../overview/lonboard.md) or the [deck.gl-raster tutorial](../overview/deckgl-raster.md)."
    ]