Make bunch of attribute selectors boolean checks

This is related to bug 1849904

chrome/curved_tabs.css

@@ -18,7 +18,7 @@ See the above repository for updates as well as full license text. */
   padding-inline: 0px !important; /* By default, proton tabs have 2px + 2px = 4px space between them */
   overflow: visible !important;
 }
-.tabbrowser-tab[visuallyselected="true"]{
+.tabbrowser-tab[visuallyselected]{
   position: relative;
   z-index: 2;
 }

chrome/hide_tabs_with_one_tab_w_window_controls.css

@@ -24,7 +24,7 @@ Window controls will be all wrong without it
 /* We'll use window controls from menubar instead */
 #TabsToolbar > .titlebar-buttonbox-container { display: none }
 /* Hide overflow button unless tabs overflow - is necessary for collpasing tabs with one tab */
-#tabbrowser-tabs:not([overflow="true"]) ~ #alltabs-button{ display: none }
+#tabbrowser-tabs:not([overflow]) ~ #alltabs-button{ display: none }
 
 #tabbrowser-tabs,
 #tabbrowser-arrowscrollbox{ min-height: 0 !important; }

chrome/multi-row_tabs.css

@@ -73,7 +73,7 @@ See the above repository for updates as well as full license text. */
 /* remove bottom margin so it doesn't throw off row height computation */
 #tabs-newtab-button{ margin-bottom: 0 !important; }
 
-#tabbrowser-tabs[hasadjacentnewtabbutton][overflow="true"] > #tabbrowser-arrowscrollbox > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
+#tabbrowser-tabs[hasadjacentnewtabbutton][overflow] > #tabbrowser-arrowscrollbox > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
   display: flex !important;
   align-items: center; /* Fx <112 compatibility */
 }

chrome/navbar_tabs_oneliner_menu_buttons_on_right.css

@@ -26,7 +26,7 @@ Window controls will be all wrong without it
 #navigator-toolbox{
   --uc-buttons-width: calc(96px + 5 * var(--toolbarbutton-outer-padding) + var(--uc-menubutton-padding,6px))
 }
-#nav-bar:not([nonemptyoverflow="true"]) > #nav-bar-customization-target{ 
+#nav-bar:not([nonemptyoverflow]) > #nav-bar-customization-target{ 
   --uc-buttons-width: calc(64px + 4 * var(--toolbarbutton-outer-padding) + 6px)
 }
 /* Override for other densities */

chrome/normal_pinned_tabs.css

@@ -30,7 +30,7 @@ See the above repository for updates as well as full license text. */
 
 .tab-icon-overlay{ display: none !important; }
 
-#tabbrowser-tabs[closebuttons="activetab"] > #tabbrowser-arrowscrollbox > .tabbrowser-tab > .tab-stack > .tab-content > .tab-close-button:not([selected="true"]){ display: none !important; }
+#tabbrowser-tabs[closebuttons="activetab"] > #tabbrowser-arrowscrollbox > .tabbrowser-tab > .tab-stack > .tab-content > .tab-close-button:not([selected]){ display: none !important; }
 
 /* Comment out or remove this if you want pinned tabs to never have close-button */
 .tab-close-button{ display: flex !important; }