Revert "Big changes to timeline buttons"

This reverts commit e05fc26f5a.

Assets/Graphics/Dark Themes/Timeline/remove_frame.png.import

@@ -1,34 +0,0 @@
-[remap]
-
-importer="texture"
-type="StreamTexture"
-path="res://.import/remove_frame.png-98800d7f0095120da61af5bff2a93e39.stex"
-metadata={
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-
-[deps]
-
-source_file="res://Assets/Graphics/Dark Themes/Timeline/remove_frame.png"
-dest_files=[ "res://.import/remove_frame.png-98800d7f0095120da61af5bff2a93e39.stex" ]
-
-[params]
-
-compress/mode=0
-compress/lossy_quality=0.7
-compress/hdr_mode=0
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-compress/normal_map=0
-flags/repeat=0
-flags/filter=false
-flags/mipmaps=false
-flags/anisotropic=false
-flags/srgb=2
-process/fix_alpha_border=true
-process/premult_alpha=false
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-process/invert_color=false
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-detect_3d=true
-svg/scale=1.0