[3.14] gh-145177: Fix Emscripten help text (GH-150874) (#150895)

Removes some stray commas in help text.
(cherry picked from commit 57d4446)

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>

Author: miss-islington

Platforms/emscripten/__main__.py

@@ -650,7 +650,7 @@ def add_cross_build_dir_option(subcommand):
         help=(
             "Path to the cross-build directory "
             f"(default: {DEFAULT_CROSS_BUILD_DIR}). "
-            "Can also be set with the CROSS_BUILD_DIR environment variable.",
+            "Can also be set with the CROSS_BUILD_DIR environment variable."
         ),
     )
 
@@ -743,7 +743,7 @@ def main():
         nargs=argparse.REMAINDER,
         help=(
             "Arguments to pass to the emscripten Python "
-            "(use '--' to separate from run options)",
+            "(use '--' to separate from run options)"
         ),
     )
     add_cross_build_dir_option(run)