Drop useless std::move of const object

...introduced with 6c8dffc19e2a570d5665344dcba6afedd3dc2e15 "compute subset of glyphs in SalLayoutGlyphsCache (tdf#139604)".

(I came across this code with an upcoming loplugin:constmove that flags
suspicious uses of std::move involving const-qualified types.)

Change-Id: Iaa356eb090cebabbed140906f0e0cee9a8039f42
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/142567
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
diff --git a/vcl/source/gdi/impglyphitem.cxx b/vcl/source/gdi/impglyphitem.cxx
index 526df69..4ca745f 100644
--- a/vcl/source/gdi/impglyphitem.cxx
+++ b/vcl/source/gdi/impglyphitem.cxx
@@ -407,7 +407,7 @@ SalLayoutGlyphsCache::GetLayoutGlyphs(VclPtr<const OutputDevice> outputDevice, c
                = makeGlyphsSubset(itWhole->second, outputDevice, text, nIndex, nLen);
            if (mLastTemporaryGlyphs.IsValid())
            {
                mLastTemporaryKey = std::move(key);
                mLastTemporaryKey = key;
#ifdef DBG_UTIL
                std::shared_ptr<const vcl::text::TextLayoutCache> tmpLayoutCache;
                if (layoutCache == nullptr)