Fix stray quote in builder.md
@@ -1845,7 +1845,7 @@ all previous `SHELL` instructions, and affects all subsequent instructions. For
RUN Write-Host hello
# Executed as cmd /S /C echo hello
- SHELL ["cmd", "/S"", "/C"]
+ SHELL ["cmd", "/S", "/C"]
RUN echo hello
The following instructions can be affected by the `SHELL` instruction when the
