[gdb/contrib] Fix shellcheck warnings in spellcheck.shHEADmaster

Fix shellcheck warnings in spellcheck.sh, found using shellcheck v0.10.0.

Ran shellcheck v0.10.0 (on a system with shellcheck version 0.8.0) using this
command from an RFC patch [1]:
...
$ ./gdb/contrib/pre-commit-shellcheck.sh ./gdb/contrib/spellcheck.sh
...

Tested on x86_64-linux

[1] https://sourceware.org/pipermail/gdb-patches/2024-November/213400.html

1 files changed, 7 insertions, 7 deletions

diff --git a/gdb/contrib/spellcheck.sh b/gdb/contrib/spellcheck.sh
index d15e124..420891f 100755
--- a/gdb/contrib/spellcheck.sh
+++ b/gdb/contrib/spellcheck.sh
@@ -269,13 +269,13 @@ parse_dictionary ()
     local i word replacement
     i=0
     for word in "${words[@]}"; do
-	replacement=${replacements[$i]}
+	replacement=${replacements[i]}
 
 	# Skip words that are already handled.  This ensures that the local
 	# dictionary overrides the wiki dictionary.
 	if [ "${words_done[$word]}" == 1 ]; then
-	    words[$i]=""
-	    replacements[$i]=""
+	    words[i]=""
+	    replacements[i]=""
 	    i=$((i + 1))
 	    continue
 	fi
@@ -283,8 +283,8 @@ parse_dictionary ()
 
 	# Skip identity rules.
 	if [ "$word" = "$replacement" ]; then
-	    words[$i]=""
-	    replacements[$i]=""
+	    words[i]=""
+	    replacements[i]=""
 	fi
 
 	i=$((i + 1))
@@ -296,7 +296,7 @@ print_dictionary ()
     local i word replacement
     i=0
     for word in "${words[@]}"; do
-	replacement=${replacements[$i]}
+	replacement=${replacements[i]}
 	i=$((i + 1))
 
 	if [ "$word" == "" ]; then
@@ -519,7 +519,7 @@ main ()
     local i word replacement
     i=0
     for word in "${words[@]}"; do
-	replacement=${replacements[$i]}
+	replacement=${replacements[i]}
 	i=$((i + 1))
 
 	if [ "$word" = "" ]; then