fix(init): don't use digits in parameter modifiers for compatibility (#11598)

Digit modifiers were introduced in zsh 5.7.1 [1]. This commit uses readily available
alternatives for backwards compatibility.

[1] https://github.com/zsh-users/zsh/commit/b8dc5a7f6d

Fixes #11598

oh-my-zsh.sh

@@ -151,8 +151,8 @@ _omz_source() {
 
   # Construct zstyle context based on path
   case "$filepath" in
-  lib/*) context="lib:${filepath:t:r}" ;;          # :t = lib_name.zsh, :r = lib_name
-  plugins/*) context="plugins:${filepath:h2:t}" ;; # :h2 = plugins/plugin_name, :t = plugin_name
+  lib/*) context="lib:${filepath:t:r}" ;;         # :t = lib_name.zsh, :r = lib_name
+  plugins/*) context="plugins:${filepath:h:t}" ;; # :h = plugins/plugin_name, :t = plugin_name
   esac
 
   local disable_aliases=0
@@ -184,7 +184,7 @@ _omz_source() {
 # Load all of the config files in ~/oh-my-zsh that end in .zsh
 # TIP: Add files you don't want in git to .gitignore
 for config_file ("$ZSH"/lib/*.zsh); do
-  _omz_source "${config_file:t2}"
+  _omz_source "lib/${config_file:t}"
 done
 unset custom_config_file