rust-gdbgui: remove excessive quotes

in commit 8dd0ec6, the `GDB_ARGS` variable was split across 3 lines. However, extra quotes were added to each line, such that the shell interprets the 3 lines as space separated strings, and tries to execute the latter two lines.
This commit simply removes the extra quotes.

Author: real-eren

src/etc/rust-gdbgui

@@ -55,9 +55,9 @@ RUST_GDBGUI="${RUST_GDBGUI:-gdbgui}"
 
 # These arguments get passed through to GDB and make it load the
 # Rust pretty printers.
-GDB_ARGS="--directory=\"$GDB_PYTHON_MODULE_DIRECTORY\"" \
-   "-iex \"add-auto-load-safe-path $GDB_PYTHON_MODULE_DIRECTORY\"" \
-   "-iex \"set substitute-path /rustc/$RUSTC_COMMIT_HASH $RUSTC_SYSROOT/lib/rustlib/src/rust\""
+GDB_ARGS="--directory=\"$GDB_PYTHON_MODULE_DIRECTORY\" \
+   -iex \"add-auto-load-safe-path $GDB_PYTHON_MODULE_DIRECTORY\" \
+   -iex \"set substitute-path /rustc/$RUSTC_COMMIT_HASH $RUSTC_SYSROOT/lib/rustlib/src/rust\""
 
 # Finally we execute gdbgui.
 PYTHONPATH="$PYTHONPATH:$GDB_PYTHON_MODULE_DIRECTORY" \