Remove USE_SOUP3

CMake had already replaced it with SOUP_VERSION, so it made no sense for
configure to insist on USE_SOUP3.

cmake/SoupVersion.cmake

@@ -34,7 +34,7 @@ elseif (NOT SOUP_VERSION)
     find_package(Soup2 QUIET)
     find_package(Soup3 QUIET)
     # Only use libsoup 3 if specifically requested or when libsoup 2 is not available
-    if (Soup3_FOUND AND NOT Soup2_FOUND OR USE_SOUP3)
+    if (Soup3_FOUND AND NOT Soup2_FOUND)
         set(SOUP_VERSION 3)
     else ()
         set(SOUP_VERSION 2)

configure

@@ -22,7 +22,7 @@ DISABLE_FAST_VAPI=
 LIB_SUFFIX=
 NO_DEBUG=
 FETCH_ONLY=
-USE_SOUP3=
+SOUP_VERSION=2
 
 EXEC_PREFIX=
 BINDIR=
@@ -113,7 +113,7 @@ while true; do
         --valac-flags ) VALAC_FLAGS="$2"; shift; shift ;;
         --lib-suffix ) LIB_SUFFIX="$2"; shift; shift ;;
         --with-libsignal-in-tree ) BUILD_LIBSIGNAL_IN_TREE=yes; shift ;;
-        --with-libsoup3 ) USE_SOUP3=yes; shift ;;
+        --with-libsoup3 ) SOUP_VERSION=3; shift ;;
         --disable-fast-vapi ) DISABLE_FAST_VAPI=yes; shift ;;
         --no-debug ) NO_DEBUG=yes; shift ;;
         --fetch-only ) FETCH_ONLY=yes; shift ;;
@@ -259,7 +259,7 @@ cmake -G "$cmake_type" \
     -DDISABLED_PLUGINS="$DISABLED_PLUGINS" \
     -DBUILD_TESTS="$BUILD_TESTS" \
     -DBUILD_LIBSIGNAL_IN_TREE="$BUILD_LIBSIGNAL_IN_TREE" \
-    -DUSE_SOUP3="$USE_SOUP3" \
+    -DSOUP_VERSION="$SOUP_VERSION" \
     -DVALA_EXECUTABLE="$VALAC" \
     -DCMAKE_VALA_FLAGS="$VALACFLAGS" \
     -DDISABLE_FAST_VAPI="$DISABLE_FAST_VAPI" \